Compounds of formula (2) to stabilize liquid crystal domains

ABSTRACT

A A compound having formula (2)  
                 
 
     wherein  
     A2 is an electron acceptor moiety;  
     C2 is a conjugated bridging moiety;  
     D2 is an electron donor moiety;  
     S2 is a hydrocarbon, a heterocyclic moiety, or a hetero-acyclic moiety;  
     a′ is an integer;  
     Z2 is a polymerizable moiety; and  
     e′ is the degree of polymerization.

BACKGROUND OF THE INVENTION

[0001] Liquid crystal displays continue to be a dominant technology forflat panel displays. Liquid crystal displays that do not use polarizers,are reflective, and have intrinsic display memory are desirable in manysituations. A number of reflective cholesteric liquid crystal displayshas recently been developed. But these conventional reflectivecholesteric liquid crystal displays typically suffer from one or more ofthe following deficiencies: switching between two states (e.g., planarstate and focal-conic state) where one or both states are not stableunder zero electric field; difficulty in fabricating black and whitedisplays since one of the states must be colored (i.e., a color otherthan white or black); viewing angle dependency; poor light reflectivity;and poor contrast between the two states. There is a need, addressed bythe present invention, to minimize or avoid one or more of abovedescribed problems.

[0002] The following documents may be relevant to the present invention:

[0003] Yang et al., U.S. Pat. No. 6,061,107.

[0004] Tamaoki et al., U.S. Pat. No. 6,103,431.

[0005] Yang et al., U.S. Pat. No. 5,847,798.

[0006] Doane et al., U.S. Pat. No. 5,691,795.

[0007] Wu et al., U.S. Pat. No. 5,625,477.

[0008] Wu et al., U.S. Pat. No. 5,661,533.

[0009] D. K. Yang et al., “Polymer-stabilized Cholesteric Textures,”Liquid Crystals in Complex Geometries Formed by polymer and porousnetworks, pp. 103-142 (Published by Taylor & Francis Ltd. 1996).

[0010] H. Yuan, “Bistable Reflective Cholesteric Displays,” LiquidCrystals in Complex Geometries Formed by polymer and porous networks,pp. 265-280 (Published by Taylor & Francis Ltd. 1996).

[0011] J. Kim et al., “White Reflective Displays from Polymer-StabilizedCholesteric Textures,” SID, p. 802-805 (1998).

[0012] D.-K. Yang et al., “Cholesteric liquid crystal/polymer dispersionfor haze-free light shutters,” Appl. Phys. Lett., Vol. 60, pp. 3102-3104(June 1992).

[0013] J. Nie et al., “Photocuring of mono- and di-functional(meth)acrylates with tris [2-(acryloyloxy)ethyl]isocyanurate,” EuropeanPolymer Journal, Vol. 35, pp. 1491-1500 (1999).

[0014] W. D. Cook, “Photopolymerization kinetics of dimethacrylatesusing the camphorquinone/amine initiator system,” Polymer, Vol. 33, pp.600-609 (1992).

[0015] I. Dierking, “Polymer Network-Stabilized Liquid Crystals,” Adv.Mater., Vol. 12, pp. 167-181 (2000).

[0016] D.-K. Yang et al., “Control of reflectivity and bistability indisplays using cholesteric liquid crystals,” J. Appl. Phys., Vol. 76,pp. 1331-1333 (1994).

[0017] E. Korenic et al., “Cholesteric Liquid Crystal Flakes—A New Formof Domain,” LLE Review, Vol. 74, pp. 139-149 (1998).

[0018] N. Tamaoki et al., “Rewritable Full-Color Recording in a PhotonMode,” Adv. Mater., Vol. 12, pp. 94-97 (2000).

[0019] W. Schuddeboom et al., “Excited-State Dipole Moments of DualFluorescent 4-(Dialkylamino)benzonitriles. Influence of Alkyl ChainLength and Effective Solvent Polarity,” J. Phys. Chem., Vol. 96, pp.10809-10819 (1992). The compound of formula 1-I described in the presentapplication is disclosed in Schuddeboom et al.

SUMMARY OF THE INVENTION

[0020] The present invention is accomplished in embodiments by providinga device comprising:

[0021] a liquid crystal composition including a liquid crystal and aliquid crystal domain stabilizing compound, wherein the liquid crystalcomposition is switchable between a strongly scattering state of a firstplurality of smaller liquid crystal domains that strongly scatters apredetermined light and a weakly scattering state of a second pluralityof larger liquid crystal domains that weakly scatters the predeterminedlight; and

[0022] a liquid crystal containment structure defining a space for theliquid crystal composition.

[0023] In further embodiments, there is provided a method comprising:

[0024] providing a liquid crystal composition including a liquid crystaland a liquid crystal domain stabilizing compound, wherein the liquidcrystal composition is switchable between a strongly scattering state ofa first plurality of smaller liquid crystal domains that stronglyscatters a predetermined light and a weakly scattering state of a secondplurality of larger liquid crystal domains that weakly scatters thepredetermined light;

[0025] changing the weakly scattering state to the strongly scatteringstate by applying a first electric field to yield an unstable state of asingle liquid crystal domain and then reducing the first electric fieldto a strongly scattering state inducing level to yield the stronglyscattering state; and

[0026] changing the strongly scattering state to the weakly scatteringstate by applying a second electric field weaker than the first electricfield but stronger than the strongly scattering state inducing level.

[0027] In embodiments of the present invention, the liquid crystal inboth the smaller liquid crystal domains and the larger liquid crystaldomains possesses helical axes that are randomly oriented.

[0028] In embodiments, there is a liquid crystal composition comprising:

[0029] (a) a liquid crystal; and

[0030] (b) a polymerized liquid crystal domain stabilizing compoundcomprising a dipolar monomer and a non-dipolar monomer.

[0031] In embodiments, there is a process comprising:

[0032] (a) forming a composition including a dipolar monomer and anon-dipolar monomer and polymerizing the dipolar monomer and thenon-dipolar monomer to result in a polymerized liquid crystal domainstabilizing compound; and

[0033] (b) adding a liquid crystal to the composition at any time suchas before, during, or subsequent to the polymerizing the dipolar monomerand the non-dipolar monomer.

[0034] A compound having formula (2)

[0035] wherein

[0036] A2 is an electron acceptor moiety;

[0037] C2 is a conjugated bridging moiety;

[0038] D2 is an electron donor moiety;

[0039] S2 is a hydrocarbon, a heterocyclic moiety, or a hetero-acyclicmoiety;

[0040] a′ is an integer;

[0041] Z2 is a polymerizable moiety; and

[0042] e′ is the degree of polymerization.

[0043] A composition comprising a liquid crystal and a compound havingformula (2)

[0044] wherein

[0045] A2 is an electron acceptor moiety;

[0046] C2 is a conjugated bridging moiety;

[0047] D2 is an electron donor moiety;

[0048] S2 is a liquid crystal compatibilizing moiety;

[0049] a′ is an integer;

[0050] Z2 is a polymerizable moiety; and

[0051] e′ is the degree of polymerization.

[0052] A device comprising:

[0053] a liquid crystal composition including a liquid crystal and aliquid crystal domain stabilizing compound, wherein the liquid crystalcomposition is switchable between a strongly scattering state of a firstplurality of smaller liquid crystal domains that strongly scatters apredetermined light and a weakly scattering state of a second pluralityof larger liquid crystal domains that weakly scatters the predeterminedlight; and

[0054] a liquid crystal containment structure defining a space for theliquid crystal composition,

[0055] wherein the liquid crystal domain stabilizing compound is acompound having formula (2)

[0056] wherein

[0057] A2 is an electron acceptor moiety;

[0058] C2 is a conjugated bridging moiety;

[0059] D2 is an electron donor moiety;

[0060] S2 is a liquid crystal compatibilizing moiety;

[0061] a′ is an integer;

[0062] Z2 is a polymerizable moiety; and

[0063] e′ is the degree of polymerization.

BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Other aspects of the present invention will become apparent asthe following description proceeds and upon reference to the Figureswhich represent exemplary embodiments:

[0065]FIG. 1 depicts an elevational simplified view of a firstembodiment of the present device where the device exhibits a stronglyscattering state;

[0066]FIG. 2 depicts a simplified magnified view of a portion of thedevice of FIG. 1;

[0067]FIG. 3 depicts an elevational simplified view of the firstembodiment of the present device where the device exhibits a weaklyscattering state;

[0068]FIG. 4 depicts a simplified magnified view of a portion of thedevice of FIG. 3;

[0069]FIG. 5 depicts an elevational simplified view of a secondembodiment of the present device where the device exhibits a stronglyscattering state;

[0070]FIG. 6 depicts a simplified magnified view of a portion of thedevice of FIG. 5;

[0071]FIG. 7 depicts an elevational simplified view of the secondembodiment of the present device where the device exhibits a weaklyscattering state;

[0072]FIG. 8 depicts a simplified magnified view of a portion of thedevice of FIG. 7;

[0073] Unless otherwise noted, the same reference numeral in differentFigures refers to the same or similar feature.

DETAILED DESCRIPTION

[0074] Unless otherwise noted the term “alkyl” encompasses both astraight chain alkyl and a branched alkyl.

[0075] The liquid crystal composition includes a liquid crystal and aliquid crystal domain stabilizing compound.

I. Liquid Crystals

[0076] The liquid crystal may be any liquid crystal capable of forming aplurality of liquid crystal domains. In embodiments, the liquid crystalmay be for example a chiral nematic (i.e., cholesteric) liquid crystalor a nematic liquid crystal. The liquid crystal may be a single compoundor a mixture of two or more different compounds.

[0077] A. Nematic Liquid Crystals

[0078] Nematic liquid crystals with positive dielectric anisotropy arecomposed of a hard core made of a polyaromatic ring and a flexiblemoiety composed of a hydrocarbon group. In embodiments, the nematicliquid crystals suitable for the purposes of this invention are composedof a hard core made of two or more monocyclic aromatic groups and aflexible moiety made of an alkyl group of variable length, which may beoptionally substituted. Most often, commercially available nematicliquid crystals are mixtures of nematic molecules.

[0079] Many suitable nematic liquid crystals are mixtures ofalkyl-biphenylnitrile or alkyl-terphenylnitrile molecules and arecommercially available and would be known to those of ordinary skill inthe art in view of this disclosure. Exemplary examples include forexample nematic liquid crystal BL mixtures available at EM Industries,Inc., BL001 (E7), BL002 (E8), BL033 (version of BL002) and BL087, and5CB (commercially available at Sigma-Aldrich). There is provided below astructural formula for nematic liquid crystals compounds that areincluded in the commercially available E7 and of 5CB:

[0080] where E7 is a mixture of compounds where n is 4, 6, and 7, and5CB is a single compound where n is 5.

[0081] B. Cholesteric Liquid Crystals

[0082] Cholesteric liquid crystals possessing a positive dielectricanisotropy with a helical pitch chosen to reflect for example in the IRor Near IR regions are suitable for the purposes of the invention. Thecholesteric liquid crystals generally can be categorized into three maintypes.

[0083] In a first main type, the cholesteric liquid crystal can be amixture of a cholesteric liquid crystal mixture and a nematic liquidcrystal in an amount sufficient to produce desired helical pitch length.Suitable cholesteric liquid crystal mixtures include for example BLmixtures available from EM Industries, Inc. (BL088, BL 90, BL94 andBL108 as a few examples). The helical pitch is tuned to the desiredrange by mixing this cholesteric liquid crystal mixture with a nematicliquid crystal described herein.

[0084] In a second main type, the cholesteric liquid crystal can be madefrom a mixture of a nematic liquid crystal and a chiral material in anamount sufficient to generate a desired pitch length. Any chiralmaterial soluble into a nematic liquid crystal is suitable for thepurposes of this invention as long as it is of high enough enantiomericor diastereoisomeric purity and it has high enough twisting power. Highperformance chiral materials are commercially available at Merck, forexample ZLI4571, ZLI4572 (R1011), S811 and R811. In particular, R1011and S811 may include compounds with the structural formulas depictedbelow.

[0085] In a third main type, the cholesteric liquid crystal can be anematic liquid crystal single compound which is also chiral (hence thename of chiral nematic liquid crystal). Optionally, the chiral nematicliquid crystal single compound can be mixed with a chiral nematic liquidcrystal mixture or with a chiral non-liquid crystal material to tune thehelical pitch to the desired value. A few examples of such singlecompound chiral nematic liquid crystals are shown below.

II. Liquid Crystal Domain Stabilizing Compounds

[0086] The liquid crystal domain stabilizing compound encompasses anycompound that: (1) induces (or allows) (along with an applied electricfield) the switching between the smaller liquid crystal domains andlarger liquid crystal domains; and (2) maintains the liquid crystaldomain size after switching when the electric field is zero. It isbelieved that the liquid crystal domain stabilizing compound placesitself mostly at the boundaries of the liquid crystal domains, and onlya low percentage of it if any is placed within the liquid crystalhelices. In embodiments, the liquid crystal domain stabilizing compoundis an organic dipolar compound such as those illustrated herein. Anorganic dipolar compound as illustrated in the formulas (1) through (6)is a conjugated structural unit possessing an electron acceptor groupand an electron acceptor group. This structural unit has a permanentdipole moment large enough so that it can be rotated by an appliedelectric field.

[0087] Liquid Crystal Domain Stabilizing Compounds of Formula (1)through Formula (6)

[0088] Formulas (1) through (6) schematically represent useful dipolarcompounds suitable for the purpose of this disclosure. While thedifferent moieties are connected schematically through single bonds,they may possess single, double or triple bonds. “Small molecule” liquidcrystal domain stabilizing compounds are exemplified by compoundscorresponding to formulas (1), (3), and (5). “Macromolecule” liquidcrystal domain stabilizing compounds which are an oligomer/polymer areexemplified by compounds corresponding to formulas (2), (4), and (6). Apolymerized liquid crystal domain stabilizing compound comprising adipolar monomer and a non-dipolar monomer (discussed herein) is alsoconsidered a “macromolecule” liquid crystal domain stabilizing compound.In embodiments, the liquid crystal domain stabilizing compounds mayabsorb at a portion of the spectrum that is compatible with theoperation of the photonic device; for instance, where the photonicdevice is a display device, the liquid crystal domain stabilizingcompounds may absorb in the UV or slightly in the visible range. Inembodiments, the liquid crystal domain stabilizing compounds arecolorless having little absorbance for example in the visible range sothat when dissolved in the liquid crystal composition in a few percents,a thin film of such a liquid crystal composition appears colorless.

[0089] The electron donor moiety (D1 through D6) may be any suitableatom or group capable of donating electrons, which in embodimentsaccording to Hammett equation may possess a negative Hammett constant(σp). In embodiments, the electron donor moiety (D1 through D6) is anatom which may require one or more additional moieties in order tofulfill its valence requirements (for example, a nitrogen atom has threevalences). In embodiments, the electron donor moiety (D1 through D6) maybe selected from the group consisting of:

[0090] (a) an atom selected from the group consisting of N, O, S, P, Cl,Br, and I, where the valence of the atom is satisfied by bonding withthe liquid crystal compatibilizing moiety (S1 through S6) and/orconjugated bridging moiety (C1 through C6) and optionally with thepolymerizable moiety (Z2, Z4, Z6);

[0091] (b) an atom selected from the group consisting of N, O, S, and Pbonded to the liquid crystal compatibilizing moiety (S1 through S6)and/or conjugated bridging moiety (C1 through C6) and optionally withthe polymerizable moiety (Z2, Z4, Z6), where the atom also is bonded toat least one other moiety to satisfy the valence of the atom;

[0092] (c) ferrocenyl;

[0093] (d) azulenyl; and

[0094] (e) at least one aromatic heterocyclic ring having from about 5to about 30 atoms (referring to number of carbon atoms andheteroatom(s)) where the heteroatom is for example oxygen (like forexample furan, benzofuran, dibenzofuran), sulfur (like for example1,4-dithiin, benzo-1,4-dithiin, dibenzo-1,4-dithiin, tetrathiafulvalene,thiophen, benzothiophen, dibenzothiophen), or nitrogen (like for examplepyrrole, indole, carbazole, pyrazole, imidazol), selenium (like forexample selenophen, benzoselenophen, dibenzoselenophen), and tellurium(like for example tellurophen, benzotellurophen, dibenzotellurophen).

[0095] In embodiments, the electron donor moiety (D1, D2) is selectedfrom the group consisting of:

[0096] (a) an atom selected from the group consisting of N, O, S, and P,where the valence of the atom is satisfied by bonding with S1/S2 andC1/C2;

[0097] (b) an atom selected from the group consisting of N, O, S, and Pbonded to S1/S2 and C1/C2, where the atom also is bonded to at least oneother moiety to satisfy the valence of the atom;

[0098] (c) ferrocenyl;

[0099] (d) azulenyl; and

[0100] (e) at least one aromatic heterocyclic ring as described herein.

[0101] The other moiety or moieties to satisfy the valence of the atomselected as the electron donor moiety (D1 through D6) may be forinstance a hydrogen atom, or a hydrocarbon group such as the following:

[0102] (a) a straight alkyl chain having for example 1 to about 20carbon atoms, particularly 1 to about 12 carbon atoms, such as pentyl,decyl and dodecyl;

[0103] (b) a branched alkyl group having for example 3 to about 40carbon atoms, particularly 3 to about 30 carbon atoms such as isopropyl,isopentyl and 2-propyl-pentyl;

[0104] (c) a cycloalkyl group having for example 3 to about 30 carbonatoms, particularly 4 to 7 carbon atoms in the cycle, such ascyclopentyl and cyclohexyl; and

[0105] (d) an aryl group, an arylalkyl group or alkylaryl group havingfor example 7 to about 30 carbon atoms such as p-methyl-benzyl,3-(p-ethyl-phenyl)-propyl and 5-(1-naphthyl)-pentyl.

[0106] The conjugated bridging moiety (C1 through C6) may be anysuitable group through which electrons can pass from the electron donormoiety (D1 through D6) to the electron acceptor moiety (A1 through A6).In embodiments, the conjugated bridging moiety (C1 through C6) is aπ-electron conjugated bridge that is composed of for example (there isno overlap among the categories (a), (b), and (c) described below):

[0107] (a) at least one aromatic ring such as one, two or more aromaticrings having for instance from about 6 carbon atoms to about 40 carbonatoms such as —C₆H₄—, and —C₆H₄—C₆H₄—;

[0108] (b) at least one aromatic ring such as one, two or more aromaticrings conjugated through one or more ethenyl or ethynyl bonds having forinstance from about 8 carbon atoms to about 50 carbon atoms such as—C₆H₄—CH═CH—C₆H₄—, and —C₆H₄—C≡C—C₆H₄—; and

[0109] (c) fused aromatic rings having for instance from about 10 toabout 50 carbon atoms such as 1,4-C₁₀H₆ and 1,5-C₁₀H₆.

[0110] The liquid crystal compatibilizing moiety (S1 through S6) may beany suitable group that increases miscibility of the liquid crystaldomain stabilizing compound with the liquid crystal. The liquid crystalcompatibilizing moiety (S1 through S6) can be 1, 2, 3, or more groups,where each group may be the same or different from each other. Theliquid crystal compatibilizing moiety (S1 through S6) may be for examplethe following:

[0111] (a) a substituted or unsubstituted hydrocarbon having for example1 to about 30 carbon atoms.

[0112] (b) a heterocyclic moiety having for example from 5 to about 15atoms (referring to number of carbon atoms and heteroatom(s), where theheteroatom can be for instance N, O, S, P, and Se. Exemplary examplesinclude: piperidine, ethyl-piperidine, methylpirrolidine.

[0113] (c) a hetero-acyclic moiety having for example from 5 to about 15atoms (referring to number of carbon atoms and heteroatom(s), where theheteroatom can be for instance N, O, S, P, and Se. Exemplary examplesinclude: glycol and polyglycol ethers, alcohol moieties like for example2-hydroxy-ethyl, and thiol moieties like for exampleethyl-2-methyl-ethyl-thioether.

[0114] When the liquid crystal compatibilizing moiety (S1 through S6) isa hydrocarbon, the hydrocarbon may be for example the following:

[0115] (a) a straight chain alkyl group having for example 2 to about 30carbon atoms, particularly 2 to about 12 carbon atoms, such as pentyl,decyl and dodecyl.

[0116] (b) a branched alkyl group having for example 3 to about 40carbon atoms, particularly 3 to about 30 carbon atoms such as isopropyl,isopentyl and 2-propyl-pentyl.

[0117] (c) at least one cycloalkyl group such as one, two or more bondedcycloalkyl groups having for example 3 to about 8 carbon atoms,particularly 4 to 7 carbon atoms in the cycle, such as cyclopentyl andcyclohexyl. Optionally, one or more hydrogen atoms of the cycloalkylgroup may be replaced with for example an alkyl group having for example1 to about 20 carbon atoms, an arylalkyl group having for example 3 toabout 30 carbon atoms, a cycloalkyl group having for example 3 to about8 carbon atoms, particularly 4 to 7 carbon atoms in the cycle, or analkylcycloalkyl group having for example 4 to about 30 carbons.

[0118] (d) an arylalkyl group or alkylaryl group having for example 7 toabout 30 carbon atoms such as p-methyl-benzyl, 3-(p-ethyl-phenyl)-propyland 5-(1-naphthyl)-pentyl.

[0119] In embodiments, the liquid crystal compatibilizing moiety (S1through S6) may be a hydrocarbon optionally substituted with for examplea liquid crystal moiety, a heterocyclic moiety optionally substitutedwith for example a liquid crystal moiety, or a hetero-acylic moietyoptionally substituted with for example a liquid crystal moiety. Theliquid crystal moiety may be composed of for example: (i) a flexibleportion—hard core moiety composed of a flexible moiety such as an alkylchain containing from about 4 to about 10 carbon atoms connected to ahard core comprised of a cyan (CN) group connected to a biphenyl orterphenyl, where the flexible portion—hard core moiety includes aconnecting moiety; or (ii) a cholesteryl group including a connectingmoiety.

[0120] To create the connecting moiety in the liquid crystal moiety, anatom (e.g, hydrogen) may be removed from a compound described herein asa liquid crystal; the removed atom is replaced with a connecting moietywhich is either an atom (like for example O, N, S, or P) or a group(like for example —O—C(O)—, —C(O)—, —O—(CH₂)_(n)—O—) having at least twoavailable valences and which is capable of bonding the liquid crystalmoiety to the rest of the liquid crystal compatibilizing moiety (S1through S6). For example, in compound 1-V, a hydrogen atom from a liquidcrystal compound CH₃—(CH₂)₄—C₆H₄—C₆H₄—CN was replaced with an O atom,resulting in liquid crystal moiety, to allow bonding with the liquidcrystal domain stabilizing compound through —CH₂ group. The whole groupis assigned as S1. The term “liquid crystal moiety” is used even if theremoval of atom or atoms from a compound described herein as a liquidcrystal results in a liquid crystal moiety which does not possess aliquid crystal nature.

[0121] The polymerizable moieties Z2, Z4 and Z6 may be any monomers thatcan be polymerized to form an oligomer/polymer. Suitable monomersinclude those having a double bond (—CH═CH₂) or triple bond capable ofbeing polymerized such as acryl or ethenyl. One or more hydrogen atomsin the monomer may be optionally replaced with for example thefollowing: (a) alkyl chains having from 1 to about 10 carbon atoms; (b)substituted alkyl chains such as alkoxy, halide substituted alkyl groups(halides like F, Cl, Br, and I), and amino-alkyl groups where the alkylmoiety has from 1 to about 10 carbon atoms. Exemplary examples ofpolymerizable moieties are H₂C═CH—C(O)—O— (acryl), H₂C═C(CH₃)—C(O)—O—(methacryl), H₂C═C(C₂H₅)—C(O)—O— (ethacryl), —CH═CH₂ (vinyl), and—C(CH₃)═CH₂. The polymerizable moiety Z_(i) (i=2, 4, 6) may be attachedto S_(i) (i=2, 4, 6), D_(i) (i=2, 4, 6), C_(i) (i=2, 4, 6), A_(i) (i=2,4, 6) or R6.

[0122] The values e′, e″ and e′″ represent the degree of polymerizationand are numbers ranging for example from 1 to about 100 or higher.

[0123] The values a′, a″, b′, b″, c′, c″ are integers such as forexample from 1 to 3.

[0124] A first exemplary group of liquid crystal domain stabilizingcompounds are encompassed by formula (1) and formula (2). In formula (2)the repetitive dipolar structural unit composed of S2, D2, C2, and A2 issimilar to compounds represented by formula (1) except that one of themoieties of the dipolar structural unit is bound to Z2.

[0125] The electron acceptor moiety (A1,A2) may be any suitable atom orgroup capable of accepting electrons. In embodiments, the electronacceptor moiety (A1,A2) is an electron withdrawing functional moietywhich according to Hammett equation possesses a positive Hammettconstant (σp). The electron acceptor moiety (A1,A2) may be for examplethe following:

[0126] (a) an aldehyde (—CO—H);

[0127] (b) a ketone (—CO—R) where R may be for example a straight chainalkyl group having for example 1 to about 20 carbon atoms, particularly1 to about 12 carbon atoms, such as methyl, ethyl, pentyl, decyl anddodecyl; a branched alkyl group having for example 3 to about 40 carbonatoms, particularly 3 to about 30 carbon atoms such as isopropyl,isopentyl and 2-propyl-pentyl, a cycloalkyl group having for example 3to about 30 carbon atoms, particularly 4 to 7 carbon atoms in the cycle,such as cyclopentyl and cyclohexyl; an arylalkyl group or alkylarylgroup having for example 7 to about 30 carbon atoms such asp-methyl-benzyl, 3-(p-ethyl-phenyl)-propyl and 5-(1-naphthyl)-pentyl;

[0128] (c) an ester (—COOR) where R may be for example a straight chainalkyl group having for example 1 to about 20 carbon atoms, particularly1 to about 12 carbon atoms, such as pentyl, decyl and dodecyl, abranched alkyl group having for example 3 to about 40 carbon atoms,particularly 3 to about 30 carbon atoms such as isopropyl, isopentyl and2-propyl-pentyl, a cycloalkyl group having for example 3 to about 30carbon atoms, particularly 4 to 7 carbon atoms in the cycle, such ascyclopentyl and cyclohexyl, an arylalkyl group or alkylaryl group havingfor example 7 to about 30 carbon atoms such as p-methyl-benzyl,3-(p-ethyl-phenyl)-propyl and 5-(1-naphthyl)-pentyl;

[0129] (d) a carboxylic acid (—COOH);

[0130] (e) cyano (CN);

[0131] (f) nitro (NO₂);

[0132] (g) nitroso (N═O);

[0133] (h) a sulfur-based group (e.g., —SO₂—CH₃; and —SO₂—CF₃);

[0134] (i) a fluorine atom;

[0135] (j) an alkene (—CH═CR₂ or —CH═CHR) where each R independently maybe for example a straight chain alkyl group having for example 1 toabout 20 carbon atoms, particularly 1 to about 12 carbon atoms, such aspentyl, decyl and dodecyl, a branched alkyl group having for example 3to about 40 carbon atoms, particularly 3 to about 30 carbon atoms suchas isopropyl, isopentyl and 2-propyl-pentyl, a cycloalkyl group havingfor example 3 to about 30 carbon atoms, particularly 4 to 7 carbon atomsin the cycle, such as cyclopentyl and cyclohexyl, an arylalkyl group oralkylaryl group having for example 7 to about 30 carbon atoms such asp-methyl-benzyl, 3-(p-ethyl-phenyl)-propyl and 5-(1-naphthyl)-pentyl;and

[0136] (k) a boron atom.

[0137] Exemplary examples of liquid crystal domain stabilizing compoundsencompassed by formula (1) are shown below.

[0138] Compounds of type 1-I and 1-II are prepared by palladiumcatalyzed coupling reaction of the bromo or iodo aromatic precursor withsecondary amines. General synthetic procedures for this widely usedcoupling reaction are known (J. P. Wolfe et al., “Room temperaturecatalytic amination of aryl iodides”, J. Org. Chem., 1997, 62, p. 6066;J. P. Wolfe et al., “Scope and limitations of the Pd/BINAP-catalyzedAmination of aryl bromides”, J. Org. Chem., 2000, 65, p. 1144.; J. F.Hartwig, “Transition metal catalyzed synthesis of arylamines and arylethers from aryl halides and triflates: scope and mechanism.” AngewandteChemie, International Edition (1998), 37(15), p. 2046; Hartwig, John F.“Carbon-Heteroatom Bond-Forming Reductive Eliminations of Amines,Ethers, and Sulfides” Accounts of Chemical Research, 1998, 31(12), 852).The disclosures of the above recited documents are totally incorporatedherein by reference. The reaction proceeds in the presence of a baselike t-BuONa, and with a palladium based catalyst formed in situ from asoluble palladium precursor like tris(dibenzylidenacetone)dipalladium(Pd₂DBA₃) and a ligand like 1,1′-bis(diphenylphosphino)ferrocene (DPPF)or 2,2′-Bis(diphenylphosphino)1-1′-binaphtyl (BINAP).

[0139] Compounds of type 1-III and 1-IV are synthesized by coupling thephenoxyde anion precursor with a bromo-alkyl derivative. The anion isprepared by using a base like K₂CO₃ (general procedure is described forexample in Organic Syntheses, Coll. Vol 3, p. 140, the disclosure ofwhich is totally incorporated herein by reference).

[0140] Compounds 1-V and 1-VI illustrate the embodiments where theliquid crystal compatibilizing moiety (S1, S2) contains a liquid crystalmoiety. Compound 1-V is synthesized by coupling the alcohol precursorwith a bromo-derivative containing the liquid crystal moiety(4-alkyl-cyano-biphenyl) in the presence of a base. Compound 1-VI issynthesized by reacting the alcohol precursor withcholesterylchloroformate in presence of an organic base liketriethylamine.

[0141] In embodiments of the present invention, there is excluded fromthe compounds of formula (1) an excluded compound defined by a′ is 2, A1is cyano, C1 is phenyl, D1 is nitrogen, and each S1 is the same alkylgroup. In embodiments, one, two or more of the following occur: a′ isother than 2; A1 is other than cyano; C1 is other than phenyl, D1 isother than nitrogen, and one or both S1 is other than a straight chainalkyl group.

[0142] Examples of macromolecular compounds of formula (2) are shownbelow. In compound 2-I, the polymerizable group Z2 is vinyl; in compound2-II, the polymerizable group is an acrylic function; and in compound2-III, the polymerizable group is a methacrylic function. In thesecases, the polymerizable group is bonded to the liquid crystalcompatibilizing group. Compound 2-IV is an example where thepolymerizable group Z2 is bonded to the electron acceptor moiety.

[0143] The dipolar structural unit (composed of S2, D2, C2, and A2) issynthesized by palladium catalyzed coupling reaction as alreadydescribed for compounds of formula (1). S2 is synthesized by reactingthe phenoxide anion with bromo-alkyl alcohols (Br—(CH₂)_(n)—OH forcompounds 2-II through 2-IV). The monomers (Z2 bonded to dipolarstructural unit composed of S2, D2, C2, and A2) are polymerized byreacting the previous alcohol derivative with acryloyl chloride (2-IIand 2-IV) or methacryloyl chloride (compound 2-III). General proceduresare known as described in G. Iftime et al. “Synthesis andCharacterization of Two Chiral Azobenzene-Containing Copolymers”Macromolecules , 2002, 35(2), 365, the disclosure of which is totallyincorporated herein by reference. The polymerization may be done insitu, by using thermal or photochemical initiation.

[0144] A second exemplary group of liquid crystal domain stabilizingcompounds is encompassed by formula (3) and (4). In compounds of formula(3) and (4) the liquid crystal compatibilizing moieties (S3, S4) arebonded to the electron acceptor moieties (A3 and A4, respectively). Informula (4) the repetitive dipolar structural unit composed of S4, D4,C4, and A4 is similar to compounds represented by formula (3) exceptthat one of the moieties of the dipolar structural unit is bound to Z4.

[0145] The electron acceptor moiety (A3, A4) may be any suitable atom orgroup capable of accepting electrons and which possess a valence capableof forming a bond with the liquid crystal compatibilizing moiety(S3,S4). In embodiments, the electron acceptor moiety (A3, A4) is anelectron withdrawing functional moiety which according to Hammettequation possesses a positive Hammett constant (σp). The electronacceptor moiety (A3, A4) may be for example the following:

[0146] (a) a carbonyl group (—CO—);

[0147] (b) a carboxyl group (—COO—);

[0148] (c) a sulphone (—SO₂—);

[0149] (d) an alkene (—CH═C(R)—) where R may be for a straight chainalkyl group having for example 1 to about 20 carbon atoms, particularly1 to about 12 carbon atoms, such as pentyl, decyl and dodecyl, abranched alkyl group having for example 3 to about 40 carbon atoms,particularly 3 to about 30 carbon atoms such as isopropyl, isopentyl and2-propyl-pentyl, a cycloalkyl group having for example 3 to about 30carbon atoms, particularly 4 to 7 carbon atoms in the cycle, such ascyclopentyl and cyclohexyl, an arylalkyl group or alkylaryl group havingfor example 7 to about 30 carbon atoms such as p-methyl-benzyl,3-(p-ethyl-phenyl)-propyl and 5-(1-naphthyl)-pentyl; and

[0150] (e) an imine group (—C═N—).

[0151] Examples of compounds corresponding to formula (3) are shownbelow:

[0152] Sulphone group (—SO₂—) in compounds 3-I and 3-IV is generated byoxidation of the corresponding sulfide (—S—) for example with hydrogenperoxide (general procedure described in Z.-S. Hu et al., “Novelpolyesters with amino-sulfone azobenzene chromophores in the mainchain”, J. Polym. Sci., Part A: Polymer Chemistry, 2000, 38, p. 2245,the disclosure of which is totally incorporated herein by reference).Alkyl ester groups are synthesized by one of the many known proceduresof esterification. A preferred mild procedure is1,3-dicyclohehylcarbodiimide (DCC) coupling of the carboxylic acidfunction with the corresponding alcohols, generally in dichloromethaneas a solvent (general procedure is described for example in J. Am. Chem.Soc., 1986, 108, p. 3112, the disclosure of which is totallyincorporated herein by reference).

[0153] Examples of macromolecular compounds corresponding to formula (4)are shown below.

[0154] Monomers corresponding to the polymeric structures of formula (4)may be synthesized by 1,3-dicyclohehylcarbodiimide (DCC) coupling of thecarboxylic acid function of the benzoic acid precursors with thecorresponding alcohols, generally in dichloromethane as a solvent(general procedure is described for example in J. Am. Chem. Soc., 1986,108, p. 3112, the disclosure of which is totally incorporated herein byreference). The polymerization may be done in situ, by using thermal orphotochemical initiation.

[0155] A third exemplary group of liquid crystal domain stabilizingcompounds is encompassed by formulas (5) and (6). In embodiments ofcompounds of formula (5) and (6), the liquid crystal compatibilizingmoiety (S5, S6) is bonded to the conjugated bridging moiety (C5,C6),through a “direct bond” (i.e., the spacer moiety (R5, R6) is absent) orthrough an optional spacer moiety (R5, R6).

[0156] In formula (6), the repetitive dipolar structural unit composedof S6, R6, D6, C6, and A6 is similar to compounds represented by formula(5) except that one of the moieties of the dipolar structural unit isbound to Z6. A5 and A6 are electron acceptor moieties identical to A1and A2. In addition, D5 and D6 are electron donor moieties identical toD3 and D4.

[0157] The electron acceptor moiety (A5,A6) may be any suitable atom orgroup capable of accepting electrons. In embodiments, the electronacceptor moiety (A5,A6) is an electron withdrawing functional moietywhich according to Hammett equation possesses a positive Hammettconstant (σp). The electron acceptor moiety (A5,A6) may be for examplethe following:

[0158] (a) an aldehyde (—CO—H);

[0159] (b) a ketone (—CO—R) where R may be for example a straight chainalkyl group having for example 1 to about 20 carbon atoms, particularly1 to about 12 carbon atoms, such as methyl, ethyl, pentyl, decyl anddodecyl; a branched alkyl group having for example 3 to about 40 carbonatoms, particularly 3 to about 30 carbon atoms such as isopropyl,isopentyl and 2-propyl-pentyl, a cycloalkyl group having for example 3to about 30 carbon atoms, particularly 4 to 7 carbon atoms in the cycle,such as cyclopentyl and cyclohexyl; an arylalkyl group or alkylarylgroup having for example 7 to about 30 carbon atoms such asp-methyl-benzyl, 3-(p-ethyl-phenyl)-propyl and 5-(1-naphthyl)-pentyl;

[0160] (c) an ester (—COOR) where R may be for example a straight chainalkyl group having for example 1 to about 20 carbon atoms, particularly1 to about 12 carbon atoms, such as pentyl, decyl and dodecyl, abranched alkyl group having for example 3 to about 40 carbon atoms,particularly 3 to about 30 carbon atoms such as isopropyl, isopentyl and2-propyl-pentyl, a cycloalkyl group having for example 3 to about 30carbon atoms, particularly 4 to 7 carbon atoms in the cycle, such ascyclopentyl and cyclohexyl, an arylalkyl group or alkylaryl group havingfor example 7 to about 30 carbon atoms such as p-methyl-benzyl,3-(p-ethyl-phenyl)-propyl and 5-(1-naphthyl)-pentyl;

[0161] (d) a carboxylic acid (—COOH);

[0162] (e) cyano (CN);

[0163] (f) nitro (NO₂);

[0164] (g) nitroso (N═O);

[0165] (h) a sulfur-based group (e.g., —SO₂—CH₃; and —SO₂—CF₃);

[0166] (i) a fluorine atom;

[0167] (j) an alkene (—CH═CR₂ or —CH═CHR) where each R independently maybe for example a straight chain alkyl group having for example 1 toabout 20 carbon atoms, particularly 1 to about 12 carbon atoms, such aspentyl, decyl and dodecyl, a branched alkyl group having for example 3to about 40 carbon atoms, particularly 3 to about 30 carbon atoms suchas isopropyl, isopentyl and 2-propyl-pentyl, a cycloalkyl group havingfor example 3 to about 30 carbon atoms, particularly 4 to 7 carbon atomsin the cycle, such as cyclopentyl and cyclohexyl, an arylalkyl group oralkylaryl group having for example 7 to about 30 carbon atoms such asp-methyl-benzyl, 3-(p-ethyl-phenyl)-propyl and 5-(1-naphthyl)-pentyl;and

[0168] (k) a boron atom.

[0169] The spacer moiety (R5, R6) may be any atom or group having atleast two available valences and which is capable of forming bonds withboth the conjugated bridging moiety (C5,C6) on one side and with theliquid crystal compatibilizing moiety (S5, S6) on the other side, andwhich may be for example the following:

[0170] (a) a direct bond (that is, the spacer moiety (R5, R6) isabsent);

[0171] (b) an oxygen atom;

[0172] (c) a sulfur containing moiety such as a sulfur atom or a sulfurgroup like —SO—, —SO₂—;

[0173] (d) a glycol ether unit having a formula —(O—CH₂—CH₂)_(n)—O—where n is an integer from 1 to about 5.

[0174] (e) a nitrogen containing moiety which is a nitrogen atom or oftype —N(R)—, where R may be for example a hydrogen, a straight chainalkyl group having for example 1 to about 20 carbon atoms, particularly1 to about 12 carbon atoms, such as pentyl, decyl and dodecyl, abranched alkyl group having for example 3 to about 40 carbon atoms,particularly 3 to about 30 carbon atoms such as isopropyl, isopentyl and2-propyl-pentyl, a cycloalkyl group having for example 3 to about 30carbon atoms, particularly 4 to 7 carbon atoms in the cycle, such ascyclopentyl and cyclohexyl, an arylalkyl group or alkylaryl group havingfor example 7 to about 30 carbon atoms such as p-methyl-benzyl,3-(p-ethyl-phenyl)-propyl and 5-(1-naphthyl)-pentyl.

[0175] Examples of compounds corresponding to formula (5) are shownbelow:

[0176] For synthesis of compounds of formulas (5) and (6), aminofunctional groups are introduced to the aromatic ring by palladiumcatalyzed coupling reaction between the bromo or iodo precursor withcorresponding amine containing at least one N—H bond using proceduressimilar to that described in J. F. Hartwig, “Transition metal catalyzedsynthesis of arylamines and aryl ethers from aryl halides and triflates:scope and mechanism,” Angewandte Chemie, International Edition (1998),37(15), p. 2046; and Hartwig, John F. “Carbon-Heteroatom Bond-FormingReductive Eliminations of Amines, Ethers, and Sulfides,” Accounts ofChemical Research, 1998, 31(12), 852, the disclosures of which aretotally incorporated herein by reference. Friedel-Crafts alkylationallows insertion of alkyl groups to the aromatic ring (textbook: Olah,George A. “Friedel-Crafts Chemistry”, 1973, the disclosure of which istotally incorporated herein by reference). For synthesis of compounds offormula (6), polymerization is being initiated thermally orphotochemically.

[0177] Examples of compounds represented by formula (6) are shown below.

[0178] There may be situations in the description of compounds offormulas (1) through (6) where a moiety can be seen as having twofunctions. This may create some difficulties in assigning the type ofmoieties for the examples shown in the structures. However, whenassigning these functions we take into account the primary functiononly. For example, in the case of compound 5-III, the —N(CH₃)₂ wasassigned as D5, but the other N atom could be viewed as having anelectron donor function as well. However, the main role of the other Natom is to allow bonding of two S5 groups, and thus it was assigned asR5. In addition, the other N atom is placed in a meta-position withrespect to the electron acceptor moiety A5, so that conjugation with A5is minimal, when compared with conjugation of D5 with A5 (para-positionallows for strong electron transfer through the conjugated bridgingmoiety from D5 to A5).

[0179] In embodiments, the liquid crystal composition can include asingle liquid crystal domain stabilizing compound. In other embodiments,the liquid crystal composition can include two, three, or more differentliquid crystal domain stabilizing compounds. In embodiments, there maybe present a combination of a macromolecule liquid crystal domainstabilizing compound and a small molecule liquid crystal domainstabilizing compound. The different liquid crystal domain stabilizingcompounds may be present in the liquid crystal composition in anysuitable equal or unequal ratio ranging for example from about 10%(first liquid crystal domain stabilizing compound): about 90% by weight(second liquid crystal domain stabilizing compound) to about 90% (firstliquid crystal domain stabilizing compound): about 10% by weight (secondliquid crystal domain stabilizing compound).

[0180] The liquid crystal composition is prepared for example by mixinga liquid crystal of a selected helical pitch with the liquid crystaldomain stabilizing compound along with one or more other optionalingredients (e.g., a dispersant and a non-dipolar co-monomer) asdescribed herein. The liquid crystal composition may be homogenized byshaking and/or stirring.

[0181] The liquid crystal domain stabilizing compound has a solubilityin the liquid crystal ranging for example from about 0.1% to 100% byweight at room temperature (about 25 degrees C.). An elevatedtemperature ranging from about 40 to about 130 degrees C. may be used tofacilitate dissolution of the liquid crystal domain stabilizing compoundin the liquid crystal. Insoluble amounts of the liquid crystal domainstabilizing compound may be optionally removed by filtration.

[0182] In embodiments, an initiator or initiators may be used tofacilitate synthesis of a “macromolecule” liquid crystal domainstabilizing compound. The initiator may be any suitable compound thatfacilitates polymerization of the monomers used in forming theoligomer/polymer. In embodiments, the polymerization is done in situ, byusing thermal or photochemical initiation. In the case of thermalinitiation classical initiators can be used and they are known to thoseskilled in the art. Examples of thermal initiators include for example2,2′-azobisisobutyronitrile (AIBN) or benzoyl peroxide. Polymerizationis carried at temperatures between about 30 to about 100 degrees C.,depending on the desired initiation rate and on the thermal initiatorused in the process. A thermal initiator may be added in an amount fromabout 0.01% to about 10%, or from about 0.1% to about 1%, with respectto the total amount of the liquid crystal composition.

[0183] Photochemical initiation may be done by using visible lightinitiation. This option may be preferable to the classical UV initiationbecause in embodiments the monomers may absorb too much in the UV range,slowing down or stopping the polymerization. Visible light initiatorsinclude for example camphoroquinone or H—Nu 470. They initiate thepolymerization when subjected to 470 nm wavelength light. Thephotochemical initiator may be added in an amount of about 0.01% toabout 3%, or from about 0.1% to about 1%, with respect to the totalamount of liquid crystal composition. When photochemical initiation isperformed, the liquid crystal composition contains also the amount ofinitiator. To prevent premature polymerization, while preparing theliquid crystal composition, in these embodiments, the mixture is heatedfor only short periods of time for example about 1 to about 5 minutes ata lower temperature ranging for example from about 30 to about 50degrees C.

[0184] A dispersant or a mixture of two or more different dispersantsmay be optionally included in the liquid crystal composition. Thedispersant(s) may be present in an amount ranging from about 0.1% toabout 20% by weight, or from about 1% to about 10% by weight, based onthe weight of the liquid crystal composition. Where two or moredifferent dispersants are used, the different dispersants may be presentin the liquid crystal composition in any suitable equal or unequal ratioranging for example from about 10% (first dispersant): about 90% byweight (second dispersant) to about 90% (first dispersant): about 10% byweight (second dispersant). In embodiments, the dispersant may be addedto those liquid crystal compositions containing a “small molecule”liquid crystal domain stabilizing compound. In other embodiments, thedispersant may be added to those liquid crystal compositions containinga “macromolecule” liquid crystal domain stabilizing compound. Thedispersant may be any suitable compound that being present at theboundaries of liquid crystal domains acts as a barrier to association ofneighboring liquid crystal domains, preventing their growth andre-alignment after the voltage is turned off. In embodiments, theaddition of a dispersant results in longer term stability of the whitestate (described herein) and in improved uniformity of the white state.The dispersant in embodiments is typically miscible with the liquidcrystal composition.

[0185] Dispersants are for instance non-aqueous surfactants which aretypically used for dispersing particles in high resistivity media.Dispersants useful for this invention are for example neutral non-ionicmolecules or oligomers containing hydrophilic and hydrophobic groups.

[0186] For compatibility with the liquid crystal composition,dispersants may possess relatively large alkyl chains, containing forexample from about 5 to about 50 carbon atoms, or from about 8 to about30 carbon atom chains. The alkyl chains can be straight or mayoptionally be branched or may contain one or more aromatic rings, toincrease compatibility with the liquid crystal composition. Dispersantsinclude, but are not limited to the following:

[0187] (a) polyoxylethylene glycol and derivatives thereof with amolecular weight from about 100 to about 3,000. Derivatives can behydroxy-terminated polyoxylethylene glycols; polyoxyethylene alkylethers with an alkyl group containing from about 1 to about 30 carbonatoms, which can be for example lauryl, cetyl, stearyl, oleyl;polyoxyethylene esters of fatty acids where the fatty acid contains fromabout 1 to about 30 carbon atoms, like for example oleic acid, lauricacid, and stearic acid.

[0188] (b) alkanolamides resulted from condensation of fatty acids withalkanolamines, having from 8 to about 60 carbon atoms.

[0189] (c) aminoxydes of general structure R₁R₂R₃NO where the R₁, R₂ andR₃ groups are independently selected and contain from about 1 to about30 carbon atoms.

[0190] (d) sorbitan esters resulting from condensation of sorbitol witha carboxylic acid ester containing from about 2 carbon atoms to about 60carbon atoms. Sorbitan esters useful for this invention are for examplesorbitan monolaurate, sorbitan monostearate, sorbitan monopalmitate,sorbitan trioleate, and sorbitan tristearate.

[0191] (e) glycerol and polyglycerol mono- and poly-esters where theester groups contain from about 2 to about 30 carbon atoms, like forexample stearate, oleate, decyl, and octyl.

[0192] (f) polydimethylsiloxane polymers with a molecular weight fromabout 100 to about 3,000, terminated with a hydroxy group or with analkyl, hydroxyalkyl or hydride group containing from about 0 to about 30carbon atoms.

[0193] (g) alkyl alcohols of a general formula R—OH where R may be for astraight chain alkyl group having for example 1 to about 20 carbonatoms, particularly 1 to about 12 carbon atoms, such as pentyl, decyland dodecyl, a branched alkyl group having for example 3 to about 40carbon atoms, particularly 3 to about 30 carbon atoms such as isopropyl,isopentyl and 2-propyl-pentyl, a cycloalkyl group having for example 3to about 30 carbon atoms, particularly 4 to 7 carbon atoms in the cycle,such as cyclopentyl and cyclohexyl, an arylalkyl group or alkylarylgroup having for example 7 to about 30 carbon atoms such asp-methyl-benzyl, 3-(p-ethyl-phenyl)-propyl and 5-(1-naphthyl)-pentyl;

[0194] (h) non-ionic halogen containing surfactants, particularlyfluorinated surfactants, possessing for example a perhalogenatedhydrocarbon group. The halogen can be F, Cl, Br, or I. The non-ionichalogen-containing surfactants suitable for the present inventiondisclosed here can be made of for example:

[0195] (h)(1) two different structural units, the first one having aperhalogenocarbon chain of the general structure, C_(n)X_(m)— (C iscarbon; X is a halogen such as F, Cl, Br, or I), where the chain may bestraight, branched or may be a perhalogenated arylalkyl chain, where nis an integer from about 1 to about 200 and m is an integer from about 3to about 600; and the second structural unit which does not containC_(n)X_(m)— units. The second structural unit may be hydrophobic when itis made of hydrocarbon chains or silicone groups, where the hydrocarbonchains can be a straight or branched alkyl, alkylaryl, arylalkyl orcycloalkyl chain containing from about 1 to about 200 carbon atoms. Thesecond structural unit can be hydrophilic when containing a watercompatible non-ionic structure. The hydrophilic structure may be forexample a poly-oxyethylated alcohol, a poly-propyleneoxyde, an alkyl, apolyhydric alcohol, and an ethanethiol derivative.

[0196] (h)(2) a single structural unit containing both a hydrophobicperhalogenocarbon chain and a hydrophilic group. Exemplary examples arefluorinated polyethers like for example poly-tetrafluoro-ethylene andpoly-hexafluoro-propeneoxide.

[0197] (i) pentaerythritol ethers, esters with alcohols or carboxylicacids having from about 1 to about 30 carbon atoms and alkoxylate ethersof pentaerythritol where alkoxylate can be ethoxylate or propoxylate.

[0198] (j) sucrose esters and ethers with a carboxylic acid or analcohol having from about 1 to about 30 carbon atoms. Optionally morethan one sucrose hydroxyl groups may be reacted with the alcohol or withthe carboxylic acid.

[0199] (k) block copolymers of two or more monomers having a molecularweight from about 100 to about 5,000. Block copolymers may be forexample polyethyleneglycol-co-polyethylene,polyethyleneglycol-co-polypropylene glycol, polyvinylalcohol-co-ethyleneand polydimethylsiloxane-co-polyethyleneglycol.

[0200] Exemplary dispersants are shown in the figure below.

[0201] where n is an integer ranging for example from 1 to about 200.

[0202] The monomers of the “macromolecule” liquid crystal domainstabilizing compounds (e.g., compounds of formulas (2), (4), and (6))are referred herein as dipolar monomers. To illustrate the structure ofthe dipolar monomers, the dipolar monomer in the compound of formula (2)corresponds to S2, D2, C2, A2, and Z2 where e′ is 1.

[0203] One, two or more different types of dipolar monomers may be usedin the synthesis of each “macromolecule” liquid crystal domainstabilizing compound. In embodiments, the dipolar monomer(s) may bepolymerized together with an optional non-dipolar monomer (one, two, ormore different types of the non-dipolar monomer) in the synthesis ofeach “macromolecule” liquid crystal domain stabilizing compound. Thedipolar monomer(s)and the optional non-dipolar monomer(s) may be used inany suitable equal or unequal ratio (by weight or by moles). Thenon-dipolar monomer may be referred herein as a non-dipolar co-monomer.The term “co-monomer” includes embodiments where there is one, two, ormore different types of non-dipolar monomers used with one, two or moredifferent types of dipolar monomers.

[0204] The non-dipolar monomer contains neither an electron donor moietynor an electron acceptor moiety, in contrast to the exemplary liquidcrystal domain stabilizing compounds of formulas (1) through (6) whichcontain an electron donor moiety and an electron acceptor moiety. Thenon-dipolar monomer may be any suitable compound that improvessolubility of the dipolar monomer and initiator into the liquid crystalcomposition. The non-dipolar monomer may be in a liquid state andcontains one or more polymerizable functional groups. It is added in anamount from about 10% to about 300% by weight with respect to the amountof dipolar monomer, or from about 10% to about 50% by weight. Inembodiments one, two or more non-dipolar monomers may be used. When morethan one non-dipolar monomer is being used, the relative amount of eachnon-dipolar monomer may be from about 5% to about 95% by weight withrespect the total amount of non-dipolar monomers. During the devicefabrication process, the dipolar monomer(s) and non-dipolar monomer(s)are polymerized together inside the liquid crystal containment structurein the presence of the liquid crystal, initiator and optionaldispersant. Due to the presence of the non-dipolar monomer(s), thestructure of the macromolecular liquid crystal domain stabilizingcompound incorporates the structural units of the non-dipolarmonomer(s). In embodiments, the resulting liquid crystal domainstabilizing compounds are random copolymers (2, 3 or more monomers)containing dipolar structural units and non-dipolar structural units. Inembodiments, the addition of the non-dipolar monomer may result in animproved uniformity of the transparent state. In embodiments without theadded non-dipolar monomer, depending on the mixing time and temperature,the transparent state may exhibit a few slightly white spots, which maybe the result of a non-homogeneous initial mixture due to some limitedmiscibility of some of the materials into the liquid crystalcomposition. These slightly white spots may disappear because ofhomogenization induced by the presence of the non-dipolar monomer.

[0205] The non-dipolar monomer may be monomers containing one or more(up to 6) polymerizable functional groups, bonded to a core. A genericformula is shown below for the non-dipolar monomer where n represent thenumber of polymerizable groups and is a number from 1 to about 6. Thepolymerizable group may be an acrylate, methacrylate, or ethacrylatepolymerizable functional group.

[0206] The monomer core may be:

[0207] (a) mono- or poly-radical (up to 6 radicals) of a hydrocarbonhaving for example 1 to about 60 carbon atoms, where the hydrocarbon maybe for example a straight chain alkyl group having for example 1 toabout 60 carbon atoms, particularly 1 to about 20 carbon atoms, such as1-pentyl, 1,2-pentyl, 1,3-pentyl, 1,5,10-decyl and 1,4,8,12-dodecyl; abranched alkyl group having for example 3 to about 50 carbon atoms,particularly 3 to about 30 carbon atoms such as isopropyl, isopentyl and2-propyl-pentyl; a cycloalkyl group having for example 3 to about 30carbon atoms, particularly with 4 to 7 carbon atoms in the cycle, suchas cyclopentyl and cyclohexyl; an arylalkyl group or an alkylaryl grouphaving for example 7 to about 60 carbon atoms such as p-methyl-benzyl,3-(p-ethyl-phenyl)-propyl and 5-(1-naphthyl)-pentyl; and a bisphenolradical. Exemplary non-dipolar monomers include nonyl methacrylate,lauril acrylate and diacrylate, 1,4-butanediol-diacrylate, 1,3-butyleneglycol diacrylate, trimethylolpropane triacrylate and propoxylatedneopentyl glycol diacrylate.

[0208] (b) glycol, polyoxylethylene glycols, alkoxylated glycols mono-and poly radicals with a molecular weight from about 100 to about 3,000.Exemplary non-dipolar monomers include ethoxylated lauryl acrylate,polyethylene glycol diacrylate, 2-(2-ethoxyethoxy)ethyl acrylate andethoxylated nonyl phenol methacrylate, and phenoxyethyl methacrylate,propoxylated neopentyl glycol diacrylate.

[0209] (c) glycerol, alkoylated and polyalcoxylated glycerol ethersmono- and poly-radical derivatives with a molecular weight from about100 to about 3,000, where alkoxylate can be ethoxylate or propoxylate.Exemplary non-dipolar monomers include glyceryl triacrylate,propoxylated glyceryl triacrylate.

[0210] (d) pentaerythritol, and alkoylated and polyalcoxylated ethersmono- and poly-radical derivatives thereof, with a molecular weight fromabout 100 to about 3,000, where alkoxylate can be ethoxylate orpropoxylate. Exemplary non-dipolar monomers include dipentaerythritolpentaacrylate, and ethoxylated dipentaerythritol pentaacrylate.

[0211] (e) epoxy and modified epoxy. Exemplary non-dipolar monomersinclude epoxy acrylate monomers which may be modified with an amine likefor example CN2100 (Sartomer product), with a fatty acids like forexample CN2101 (Sartomer product), and with chlorine like for example CN2201 (Sartomer product).

[0212] (f) radicals of alkoxylated and polyalcoxylated ethersincorporating heteroatom-containing hydrocarbon groups, with a molecularweight from about 100 to about 3,000. Exemplary non-dipolar monomersinclude tris-(2-hydroxy ethyl) isocyanurate triacrylate, alkoxylatedtetrahydrofurfuryl acrylate.

[0213] (g) urethane and derivatives thereof with a molecular weight ofabout 100 to 3,000. Exemplary examples of non-dipolar monomers are forexample CN-962 (urethane acrylate, Sartomer product), CN-1963 (urethanemethacrylate, Sartomer product) and CN-963B80 (urethane acrylate blendedwith SR-238, Sartomer product).

[0214] In embodiments, using both the non-dipolar co-monomer and thedispersant may be desired.

[0215] Regarding the amounts of the various ingredients to employ in thepresent invention, the following illustrative proportions are provided:

[0216] (a) liquid crystal: about 80% to about 98% by weight based on theweight of the liquid crystal composition;

[0217] (b) liquid crystal domain stabilizing compound: about 2% to about20% by weight based on the weight of the liquid crystal composition;

[0218] (c) initiator: about 0.2% to about 3% by weight based on theweight of the liquid crystal composition;

[0219] (d) dispersant: about 0.5% to about 5% by weight based on theweight of the liquid crystal composition;

[0220] (e) non-dipolar co-monomer: about 1% to about 3% by weight basedon the weight of liquid crystal composition.

[0221] An illustrative example is as follows, where the percentages byweight are based on the weight of all ingredients in the liquid crystalcomposition:

[0222] (a) liquid crystal: 95%

[0223] (b) liquid crystal domain stabilizing compound: 3%

[0224] (c) initiator: 0.5%

[0225] (d) dispersant: 1%

[0226] (e) non-dipolar co-monomer: 0.5%.

[0227] The present liquid crystal composition is capable of forming astrongly scattering state of a first plurality of smaller liquid crystaldomains that strongly scatters a predetermined light wavelength orwavelengths and a weakly scattering state of a second plurality oflarger liquid crystal domains that weakly scatters the predeterminedlight wavelength or wavelengths.

[0228] The existence of liquid crystal domains will now be discussed. Inboth strongly and weakly scattering states, the helical axes of theliquid crystal are not all perfectly oriented parallel to one another.In fact, in embodiments, the helical axes of the liquid crystal may bemore or less randomly oriented. Domain boundaries appear at the edgeswhere orientation of helical axes changes. This polydomain state isknown as a focal-conic state.

[0229] In embodiments, for both the strongly scattering state and theweakly scattering state, the liquid crystal domains contact one another(i.e., no void among them) and in the case of larger domains they have alamellar shape. In the case of smaller domains, the difference betweenlength and width is less significant. In a device where the volumeoccupied by the liquid crystal composition is typically fixed, thenumber of liquid crystal domains is inversely proportional with thedomain size (i.e., domain number decreases with increased domain size ifthe domains contact one another with no voids between them). Inembodiments, the smaller liquid crystal domains have a domain size rangeof for example from about 0.5 to about 10 micrometers, or any subsetthereof such as from about 5 to about 10 micrometers. In embodiments,the larger liquid crystal domains have a domain size range as follows:(a) a length ranging for example from about 10 to about 40 micrometers,or any subset thereof such as from about 25 to about 30 micrometers; and(b) a width ranging for example from about 5 to about 20 micrometers, orany subset thereof such as from about 5 to about 10 micrometers.

[0230] The phrase “strongly scattering state” refers to transmission of0% to about 20%, particularly, 0% to about 10% of the predeterminedlight wavelength or wavelengths and the phrase “weakly scattering state”refers to transmission of about 80% to 100%, particularly about 90% to100% of the predetermined light wavelength or wavelengths. Thisdefinition implies that the back of the device is transparent whencharacterization by transmission spectroscopy is performed. Inembodiments, values outside the light transmission ranges describedherein are encompassed if there is sufficient difference in lightscattering between the “strongly scattering state” and the “weaklyscattering state” to enable the present device to function as forexample a photonic device such as for instance a display device, anoptical digital storage device, an optical switching device, or someother photonic device. The extent of light scattering depends upon anumber of factors such as for example the predetermined light wavelengthor wavelengths, the liquid crystal domain size, the particular liquidcrystal, and the number of liquid crystal domains.

[0231] As noted herein, the phrases “weakly scattering state” and the“strongly scattering state” encompass a range of light transmissionvalues. Consequently, for a particular liquid crystal and apredetermined light wavelength or wavelengths, there may be a singleliquid crystal domain size range or a plurality of liquid crystal domainsize ranges that yield the “weakly scattering state” and there may be asingle liquid crystal domain size range or a plurality of liquid crystaldomain size ranges that yield the “strongly scattering state.” Thus, the“weakly scattering state” encompasses one or a plurality of liquidcrystal domain states having the desired weakly light scatteringattribute, where these various weakly scattering states may differ inthe liquid crystal domain size range. Similarly, the “stronglyscattering state” encompasses one or a plurality of liquid crystaldomain states having the desired strongly light scattering attribute,where these various strongly scattering states may differ in the liquidcrystal domain size range.

[0232] When the “weakly scattering state” and the “strongly scatteringstate” are described as being switchable between each other, thisencompasses the following embodiments:

[0233] (a) where the “weakly scattering state” has generally the sameliquid crystal domain size range every time there is a switch to the“weakly scattering state,” and where the “strongly scattering state” hasgenerally the same liquid crystal domain size range every time there isa switch to the “strongly scattering state” (this embodiment may beaccomplished for example by not varying from the procedures used toproduce each of the multiple “weakly scattering states” and by notvarying from the procedures used to produce each of the multiple“strongly scattering states”);

[0234] (b) where during repeated switching between the “stronglyscattering state” and the “weakly scattering state,” the liquid crystaldomain size range of the multiple “weakly scattering states” may differ(this embodiment may be accomplished by using for example differentelectric field strengths among the multiple “weakly scattering states”);and

[0235] (c) where during repeated switching between the “stronglyscattering state” and the “weakly scattering state,” the liquid crystaldomain size range of the multiple “strongly scattering states” maydiffer (this embodiment may be accomplished by using for exampledifferent electric field strengths among the multiple “stronglyscattering states”).

[0236] The number of liquid crystal domains can be for example in thehundreds, thousands, tens of thousands, or millions with a range ofdomain sizes. In embodiments, a number of the liquid crystal domainssuch as for example about 70% to 100% of the liquid crystal domains maychange in size when switching occurs. However, in embodiments, some ofthe liquid crystal domains will remain unchanged in size when switchingoccurs.

[0237] In embodiments where the device is a display device, the extentof light reflectance by the display device may be determined byreflectance spectrophotometry measured for instance for the wholevisible spectrum (380 nm to 730 nm). Gretag spectrophotometer at normalangle with respect to the device surface may be used in order to measurethe reflectance of the inventive devices, such light reflectancemeasurement procedures being well known to those skilled in the art.

[0238] The present device includes a liquid crystal containmentstructure defining a space for the liquid crystal composition. The spacehas a thickness ranging for example from about 5 micrometers to about 50micrometers. In embodiments, the predetermined light enters the space(and the liquid crystal composition) at an orthogonal angle or any otherappropriate angle.

[0239] The structure may be substantially transparent to thepredetermined light to allow the predetermined light to reach the liquidcrystal composition. The phrase “substantially transparent” when used todescribe the structure encompasses one or more substantially transparentsections and/or one or more openings. In addition, the phrase“substantially transparent” when used to describe the structure refersto, in embodiments, the transmission of about 60% to 100% of thepredetermined light that enters the structure; light transmission valuesoutside this exemplary range are encompassed where such lighttransmission values enable the present device to function as for examplea display device, an optical digital storage device, an opticalswitching device, or some other photonic device.

[0240] In embodiments, the device also includes a colored (that is,non-white) surface positioned to absorb a portion of the predeterminedlight that passes through the liquid crystal composition in the weaklyscattering state where the liquid crystal composition may be disposedbetween substantially transparent sections of the structure and thecolored surface. The extent of light absorption by the colored surfacemay be such that an observer sees the predetermined color (black, gray,red, green, or any other desired color) when looking through thesubstantially transparent sections of the structure and the liquidcrystal composition at the colored surface. The colored surface may befor example a painted layer or a separate colored layer. The coloredsurface (whether a painted layer or a separate colored layer) needs tobe thick enough so that it is not transparent to the incident light,i.e., a viewer does not see anything through a device after painting orplacing the colored layer. A separate colored layer may be for examplefabricated from colored glass, colored paper or colored plastic. Thecolored layer may be attached to or held in place to the structure viafor example an adhesive or a clamp

[0241] In embodiments, the structure is substantially transparent to thepredetermined light to allow entry of the predetermined light into thestructure, through the liquid crystal composition, and exit of thepredetermined light from the structure in the weakly scattering state.

[0242] In embodiments, the liquid crystal containment structure iscomposed of two flat sections that are scaled around their edges andseparated by spacers to define the space for the liquid crystalcomposition. The sections may be transparent, fabricated from forexample glass or plastic materials. The internal sides of thetransparent sections are coated with a conductive electrode layer, whichconstitute the electrodes required to apply different electric fields inorder to switch the device to different states. The conductive electrodelayers are substantially transparent. Typical materials for transparentelectrodes include indium-tin oxide and the like, where the transparentelectrodes have a resistivity of for example less than or equal to about125 ohm/sq. Spacers used to control the thickness of the space for theliquid crystal composition may be glass fibers or polymeric fibers orspheres. Fabrication of the liquid crystal containment structure may beaccomplished by first dispensing glue on the edges of one of thesections, placing the second section on top, followed by curing toharden the glue. The glue can be either UV photo-curable like forexample Norland Optical Adhesives or thermo-curable like for exampleepoxy glues. A small opening is left unsealed, which is used for vacuumfilling of the liquid crystal composition. Complete sealing of thefilled liquid crystal containment structure can be accomplished with athermally curable epoxy glue. In the case of a device containingmonomers for a “macromolecule” liquid crystal domain stabilizingcompound, polymerization of such monomers to obtain the “macromolecule”liquid crystal domain stabilizing compound is obtained by exposure tolight or by heating (in the case of thermal initiation).

[0243] Sealing not only provides structural stability to the liquidcrystal containment structure but also may prevent air leakage into thecontainment structure except at the opening and this enablesair-filling.

[0244] Where the present device is used for example as a white and blackdisplay, an observer sees white as the color produced by device in thestrongly scattering state where the predetermined light is in thevisible spectrum.

[0245] As used herein, “white state” and “black state” refer to theperceived color of the reflected ambient light from the stronglyscattering state composed of the smaller liquid crystal domains (for the“white state”) and from the weakly scattering state composed of thelarger liquid crystal domains (for the “black state” where the coloredsurface in the device is black).

[0246] As used herein, the “transparent state” refers to weaklyscattering state composed of the larger liquid crystal domains which isreferred as “black state” when the colored surface is black.

[0247] In embodiments, the device may optionally include one or moremirrors and/or one or more fiber optic wires (external to the device orincorporated into the device) to facilitate the transmission of thepredetermined light within the device.

[0248] A light source (external to the present device or incorporatedinto the device) may generate the predetermined light. Any suitablelight wavelength or wavelengths may be employed such as thosewavelengths useful for a display device, an optical digital storagedevice, an optical switching device, or some other photonic device. Thesuitable wavelength or wavelengths may be in any part of the spectrumsuch as the visible spectrum ranging for example from about 380 nm toabout 730 nm, and the infrared spectrum ranging for example from about730 nm to about 2000 nm, particularly from about 800 nm to about 1700nm. The light source may be for example a laser, a light bulb, orsunlight. In the context of an optical switching device, the“predetermined light” refers to the wavelength(s) of the light which isturned ON or turned OFF by the optical switch device. When the device isused as a display, the “predetermined light” is ambient visible light.

[0249] An electric field generating apparatus (external to the presentdevice or incorporated into the device) produces the desired electricfields. The electric field generating apparatus may be a single deviceor two or more devices that can produce the desired electric fields. Theelectric field generating apparatus can produce an electric fieldranging for example from 0 V/μm to about 10 V/μm, particularly fromabout 1 V/μm to about 10 V/μm, a voltage ranging from 0 V to about 250V, particularly from about 20 V to about 120 V.

[0250] To change either the initial state (i.e., prior to theapplication of any electric field to the liquid crystal composition) orthe weakly scattering state to the strongly scattering state, theelectric field generating apparatus produces for instance a firstelectric field of sufficient strength to form an unstable state of asingle liquid crystal domain (that is, no separate liquid crystaldomains are visually observed). The first electric field can be a valueranging for example from about 2 V/μm to about 10 V/μm, particularlyfrom about 3 V/μm to about 7 V/μm. The first electric field is appliedfor a time ranging for example from about 1 msec to about 1 sec,particularly from about 10 msec to about 100 msec. The first electricfield is then reduced to a strongly scattering state inducing level toyield the strongly scattering state. The liquid crystal domainsspontaneously arrange into the strongly scattering state at the stronglyscattering state inducing level. The strongly scattering state inducinglevel corresponds to an electric field ranging for example from 0% toabout 30% of the first electric field, particularly from 0 to about 10%of the first electric field. For instance, the strongly scattering stateinducing level corresponds to an electric field ranging from 0% to about5% of the first electric field, particularly 0%. The strongly scatteringstate inducing level is applied for a time ranging for example fromabout 10 msec to about 1 sec, particularly from about 10 msec to about100 msec.

[0251] To change either the initial state (i.e., prior to theapplication of any electric field to the liquid crystal composition) orthe strongly scattering state to the weakly scattering state, theelectric field generating apparatus produces for instance a secondelectric field weaker than the first electric field but stronger thanthe strongly scattering state inducing level. The second electric fieldis greater than the strongly scattering state inducing level by a valueranging for example from about 30% to about 70%, particularly from about40% to about 60% of the difference between the first electric field andthe strongly scattering state inducing level. For instance, the secondelectric field may be from about 0.5 V/μm to about 4 V/μm, particularlyfrom about 0.75 V/μm to about 3 V/μm. The second electric field isapplied for a time ranging for example from about 10 msec to about 1sec, particularly from about 20 msec to about 200 msec.

[0252] In embodiments, the switching between the weakly scattering stateand the strongly scattering state may be accomplished without anysignificant degradation of the device for any desired number of timessuch as for example hundreds, thousands, millions of times or higher.

[0253] In embodiments, in the initial state just after devicefabrication but before application of any electric field, the liquidcrystal composition may be mostly in a planar state, i.e., helicesaligned perpendicularly to the surfaces of the liquid crystalconfinement structure used to define the space for the liquid crystalcomposition. A few focal-conic domains of large size coexist with theplanar state (that is, the liquid crystal composition in the initialstate may be considered a single liquid crystal domain with a few“imperfections”). This initial state is suitable for measuring thereflected wavelength of the liquid crystal helices, which is an indirectmeasurement of the helical pitch of the liquid crystal. This initialstate may be used in order to optimize the helical pitch of the liquidcrystal. In fact, in the initial state, the liquid crystal compositionmay be transparent to all wavelengths except to the wavelengthcorresponding to the helical pitch of the liquid crystal. Inembodiments, after applying the first or the second electric field asdescribed in this invention, the liquid crystal composition may neverreturn to this initial state.

[0254] In embodiments, the strongly scattering state and/or the weaklyscattering state may be stable. The term “stable” refers to the factthat each of these states is capable of maintaining its characteristicsas strongly scattering or weakly scattering for a period of time afterthe applied electric field is turned off. The term “stable” also may beto describe a “white state” and a “black state” which refers to the factthat each of these states is capable of maintaining its color for aperiod of time after the applied electric field is turned off, where theperceived color (white/black) is of the reflected light from thestrongly scattering state (for the white state) and from the weaklyscattering state (for the black state where the colored surface in thedevice is black). Within the time frame for “stable,” some “decay” mayoccur over time such as a change in the liquid crystal domain size rangebut such a change in embodiments should not change a strongly scatteringstate to a weakly scattering state or a weakly scattering state to astrongly scattering state. The length of time that the stronglyscattering state and the weakly scattering state are “stable” depends ona number of factors such as the type of liquid crystal, the type andconcentration of the liquid crystal domain stabilizing compound, and thelike. In embodiments, the length of time that the strongly scatteringstate and the weakly scattering state are “stable” after the appliedelectric field is turned off is sufficient for the device to function asany type of photonic device such as a display device, an opticalswitching device, an optical digital storage device, and the like, sucha “stable” time period lasting for example from at least about 10seconds and up such as minutes, perhaps hours, days, or even longer,particularly from about 10 seconds to about 20 minutes. For example, fora display device, the term “stable” means a long enough time so that adocument written by applying a number of electric fields can be readwhen the power is turned off. In other words, the display maintains thewritten image for a long enough time to be readable at zero voltage. Forexample, the image is stable for a minimum of about 10 seconds. Somelittle decay may occur within the specified time, but this does notaffect significantly the image, which is still perfectly readable. In anoptical switching device, the term “stable” means the stronglyscattering state and the weakly scattering state are capable ofpersisting until the next generation of an electric field to perform theswitching.

[0255] Bistability allows fabrication of low power consuming devices,which are suitable for design of integrated optics circuits. Still,another important use of bistable devices is in optical digital storage,since after writing, the information is stable and can be read with aprobe beam.

[0256] The term “unstable” when referring to the unstable state of thesingle liquid crystal domain produced by the first electric field meansthat this state immediately changes when the applied electric field isturned off or when the applied electric field is significantly lowered,for example, by at least about 50%. Immediately means less than about0.5 seconds. In other words, this state is lost so fast so that anobserver may not detect it after the applied electric field is turnedoff. In embodiments of the present invention, this unstable stateproduced by the first electric field may have the followingcharacteristics: (a) a single liquid crystal domain (with no“imperfections”); (b) a homotropic state having an ordered structurewith no liquid crystal helices; (c) liquid crystal molecules areperpendicular to the surfaces defining the space for the liquid crystalcomposition; and (d) transparent to all light wavelengths.

[0257] FIGS. 1-4 depict an embodiment of the present device useful as adisplay device 2A, particularly for example a white and black display.The device is composed of a liquid crystal containment structure 4A. Theliquid crystal containment structure is composed of a top transparentflat section 8A and a bottom transparent flat section 1A wherein the twoflat sections are sealed around their edges and are separated by spacers(not shown) to define a space 6A for the liquid crystal composition. Theinternal side of the top section is coated with a transparent conductiveelectrode layer 28A and the internal side of the bottom section iscoated with a transparent conductive electrode layer 30A to provide theelectrodes needed to apply the electric field for switching. Theexternal side of bottom section includes a colored surface 12. Theliquid crystal composition 14A is disposed in the space. An electricfield generating apparatus 16A is coupled to the two electrode layers.

[0258] FIGS. 1-2 illustrate the strongly scattering state where thepredetermined light 24A is scattered by the plurality of smaller liquidcrystal domains 18A. To an observer looking in the direction of thecolored surface 12, the colored surface appears white (where thepredetermined light is in the visible spectrum). FIG. 2 depicts amagnified view of the liquid crystal composition in the stronglyscattering state of a plurality of smaller liquid crystal domains 18A,where the smaller domains are in a random orientation. The orientationof the smaller liquid crystal domains is the orientation of the helices22A inside the domains.

[0259] FIGS. 3-4 illustrate the weakly scattering state of a pluralityof larger liquid crystal domains where the predetermined light 24Apasses through the structure 4A to the colored surface 12 where thepredetermined light is weakly scattered by the plurality of the largerliquid crystal domains 20A. The colored surface 12 absorbs a portion ofthe predetermined light. To an observer looking in the direction of thecolored surface, the colored surface has the color of the coloredsurface (where the predetermined light is in the visible spectrum). FIG.4 depicts a magnified view of the liquid crystal composition in theweakly scattering state of a plurality of larger liquid crystal domains20A where the larger domains are in a random orientation. Theorientation of the larger liquid crystal domains is the orientation ofthe helices 22A inside the domains.

[0260] FIGS. 5-8 depict an embodiment of the present device useful as anoptical switching device 2B between two optical fibers (not shown) wherea light signal can be transmitted or not from one optical fiber to thenext optical fiber in a controlled manner. The device is composed of aliquid crystal containment structure 4B. The liquid crystal containmentstructure is composed of a top transparent flat section 8B and a bottomtransparent flat section 10B wherein the two flat sections are sealedaround their edges and are separated by spacers (not shown) to define aspace 6B for the liquid crystal composition. The internal side of thetop section is coated with a transparent conductive electrode layer 28Band the internal side of the bottom section is coated with a transparentconductive electrode layer 30B to provide the electrodes needed to applythe electric field for switching. The liquid crystal composition 14B isdisposed in the space. An electric field generating apparatus 16B iscoupled to the two electrode layers. The device 2B includes a receiver26 to receive any predetermined light that passes through the structure4B. The receiver 26 may be separate from or coupled to structure 4B. Thereceiver may for example amplify the light signal, act as a switch oract as a transducer converting the light signal into another signal type(e.g., sound, electrical impulse, mechanical and the like). The receiver26 is commercially available from a number of vendors.

[0261] FIGS. 5-6 illustrate the strongly scattering state where thepredetermined light 24B is scattered by the plurality of smaller liquidcrystal domains and little if any of the predetermined light reaches thereceiver 26. FIG. 6 depicts a magnified view of the liquid crystalcomposition in the strongly scattering state of a plurality of smallerliquid crystal domains 18B. The orientation of the smaller liquidcrystal domains is the orientation of the helices 22B inside thedomains.

[0262] FIGS. 7-8 illustrate the weakly scattering state where thepredetermined light 24B passes through the structure 4B to the receiver26 (the predetermined light is weakly scattered by the plurality of thelarger liquid crystal domains). FIG. 8 depicts a magnified view of theliquid crystal composition in the weakly scattering state of a pluralityof larger liquid crystal domains 20B. The orientation of the largerliquid crystal domains is the orientation of the helices 22B inside thedomains.

[0263] The invention will now be described in detail with respect tospecific exemplary embodiments thereof, it being understood that theseexamples are intended to be illustrative only and the invention is notintended to be limited to the materials, conditions, or processparameters recited herein.

[0264] In the examples below, the following guidelines are followedunless otherwise noted:

[0265] (1) All percentages and parts are by weight.

[0266] (2) The switching in the devices between the weakly scatteringstate and the strongly scattering state is accomplished at roomtemperature, i.e., about 25 degrees C.

[0267] (3) All the liquid crystal containment structures were preparedand filled in the same manner as described in Example 7.

[0268] (4) Cholesteric liquid crystals sold under the “BL” seriesdesignation such as BL118 and BL087 are available from EM Industries,Inc.

[0269] (5) “Paper examples” describing illustrative work not actuallyperformed are written in the present tense (examples 3, 4, 5 and 6),whereas actual experimental examples are written in the past tense.

EXAMPLE 1 Preparation of Liquid Crystal Domain Stabilizing Compound 1-I

[0270] About 0.23 g of tris(dibenzylidenacetone)dipalladium(Pd₂DBA₃.CHCl₃) and about 0.25 g of 1,1′-bis(diphenylphosphino)ferrocene(DPPF) were dissolved under inert atmosphere in 100 ml of toluene(freshly distilled and degassed from sodium/benzophenone). The solutionwas stirred for 10 min at room temperature. About 2.0 g of 4-bromobenzonitrile was added as solid to this mixture and the solution wasstirred for about 15 min. About 1.48 g of solid t-BuONa then 3.43 g ofdidecylamine were added to the previous mixture. The mixture was heatedat 90-100° C. for at least 20 hours. After cooling down, the organicphase was diluted with diethylether, washed with water, dried overMgSO₄, and solvent were removed with a rotaevaporator. The crude productwas purified by column chromatography on silicagel by using a mixture ofhexane/diethyl ether as eluent and after sovents evaporation wasobtained as a pale yellow low melting point solid. The product was pureas tested by 1H-NMR and 13C-NMR spectroscopy.

EXAMPLE 2 Preparation of Liquid Crystal Domain Stabilizing Compound 2-II

[0271] a. Synthesis of 4-NC—C₆H₄—O—(CH₂)₃—OH. About 2.14 g of4-cyanophenol and 2.67 g of anhydrous K₂CO₃ were dissolved under inertatmosphere in 50 ml of acetone (distilled from K₂CO₃). About 1.95 ml of3-bromo-1-hexanol was added and the solution was refluxed for at least20 hours. Solids were filtered off, the crude product was dissolved inmethylene chloride, washed with aqueous solution of NaOH (10%), thenwashed with water. The organic phase was dried over MgSO₄, and thesolvent was removed with a rotaevaporator. The pure product was obtainedby flash chromatography on silicagel with ethyl acetate/hexane solvents.

[0272] b. Synthesis of the monomer 4-NC—C₆H₄—O—(CH₂)₃—O—(O)C—CH═CH₂.About 1.0 g of 4-NC—C₆H₄—O—(CH₂)₃—OH was dissolved in 15 ml oftetrahydrofuran (THF) (distilled from sodium/benzophenone) and 3 ml oftriethylamine. The solution was cooled at 0° C., then a solutioncontaining about 0.67 ml of acryloyl chloride in 10 ml of THF was addeddrop-by-drop for a period of at least 30 min, under inert atmosphere.The solution was allowed to warm at room temperature and stirred for atleast 24 hours. The solids were filtered off, the solvents were removedwith an rotaevaporator. Pure monomer was obtained by recrystallization(ethanol/water) or by flash chromatography on silicagel.

[0273] c. The actual polymeric structure was obtained from this monomer,in situ, by illumination of the cell with visible light after the liquidcrystal composition containing the monomer and initiator was prepared,and is explained in Example 9.

EXAMPLE 3 Preparation of Liquid Crystal Domain Stabilizing Compound 3-II

[0274] 4-O₂N—C₆H₄—OOC—(CH₂)₉—CH₃ is synthesized by coupling of4-nitrophenol with 1-decanol in presence of 1,3-dicyclohehylcarbodiimide(DCC), using a standard procedure (J. Am. Chem. Soc., 1986, 108, p.3112, the disclosure of which is totally incorporated herein byreference). About 5.3 g of 4-O₂N—C₆H₄—OOC—(CH₂)₉—CH₃, 0.90 g of cobaltsulfide (CoSx) paste containing 0.055 g of Co., and 30 ml of ethylacetate are placed into a reactor. The mixture is hydrogenated at 110°C. until the theoretical amount of hydrogen was consumed (about 2hours). After depressurizing, the reaction mixture is filtered torecover the catalyst, solvent is removed on a rotary evaporator. Theproduct is purified by recrystallization.

EXAMPLE 4 Preparation of Liquid Crystal Domain Stabilizing Compound 4-II

[0275] a. HOOC—C₆H₄—O—(CH₂)₆—OH. A mixture of 19.4 g of 4-hydroxybenzoicacid and 21 g of KOH in a mixture of 20 ml of water and 45 ml of ethanolis heated at 80° C. with stirring. To this solution is added a solutionof 35 ml of 6-chloro-hexanol dissolved in 10 ml ethanol, dropwise inabout one hour. The mixture is refluxed while stirring for at least 20hours. The solution is concentrated and washed with diethyl ether. Theaqueous phase is acidified with 60 ml of concentrated HCl solution inwater. The large amount of precipitate is filtered and dried, then thepure product is obtained by recrystallization from hot ethanol.

[0276] b. CH₂═CH—COO—(CH₂)₆—O—C₆H₄—COOH. About 5.0 g ofHOOC—C₆H₄—O—(CH₂)₆—OH is dissolved under inert atmosphere in 60 ml ofdistilled THF and 8 ml of distilled triethylamine. The solution iscooled at 0° C., then a solution of 1.7 ml of acryloyl chloride in 10 mlof THF is added drop-by-drop. The mixture is allowed to stir at roomtemperature for at least 24 hours. The solids are filtered off, thesolvents are removed with an rotary evaporator. Crude product ispurified by recrystallization (ethanol/water) or by flash chromatographyon silicagel.

[0277] c. CH₂═CH—COO—(CH₂)₆—O—C₆H₄—COO—(CH₂)₄—CH₃. About 2 g ofCH₂═CH—COO—(CH₂)₆—O—C₆H₄—COOH with 0.70 g of n-propanol and 0.090 g of4-dimethylaminopyridine DMAP are dissolved in 25 ml of methylenechloride. About 7.5 ml of 1M solution of 1,3-dicyclohehylcarbodiimideDCC in methylene chloride are being added and the solution is stirredfor at least 15 hours. The precipitate is removed by filtration, theorganic phase is washed with water, solvent are removed on a rotaryevaporator. The crude product is purified by column chromatography onsilicagel with ethyl acetate/hexane mixture of solvents.

[0278] d. The actual polymeric structure is obtained from this monomer,in situ, by illumination of the cell with visible light after the liquidcrystal composition containing the monomer and initiator is preparedusing procedures similar to that described in Example 9.

EXAMPLE 5 Preparation of Liquid Crystal Domain Stabilizing Compounds 5-Iand 5-II

[0279] Compound 5-I is synthesized by Friedel-Crafts alkylation of4-methoxy-benzonitrile with butanol in presence of AlCl₃ as a catalyst.General experimental procedure is described in J. Am. Chem. Soc., 60,1938, p. 1421, the disclosure of which is totally incorporated herein byreference.

[0280] Compound 5-II is synthesized by reacting[4-Br-(2,5-diethyl)-phenyl]-N,N-dimethyl aniline with CuCN/NaCN indimethylformamide (DMF) (Dyes and Pigments, 47(1-2), pp.117-127; 2000,the disclosure of which is totally incorporated herein by reference).

EXAMPLE 6 Preparation of Liquid Crystal Domain Stabilizing Compound 6-II

[0281] a. O₂N—C₆H₄—O—CH₂CH₂—OH is synthesized by refluxing 2.3 g of4-nitro-phenol with 1.8 ml of 2-bromo-ethanol in presence of 2.5 g ofK₂CO₃ in acetone. Solids are filtered off, the crude product isdissolved in methylene chloride, wash with aqueous solution of NaOH(10%), then wash with water. The organic phase is dried over MgSO₄, andthe solvent is removed with a rotary evaporator. The pure product isobtained by flash chromatography on silicagel with ethyl acetate/hexanesolvents.

[0282] b. O₂N—C₆H₄—O—CH₂CH₂—OOC—CH═CH₂ is obtained by reacting 2.0 g ofO₂N—C₆H₄—O—CH₂CH₂—OH with 0.7 ml of acryloyl chloride in THF for atleast 24 hours. Crude product is purified by recrystallization(ethanol/water) or by flash chromatography on silicagel.

[0283] c. O₂N—C₆H₄—O—CH₂CH₂—OOC—CH═CH₂ is coupled by Friedel-Craftsalkylation butanol in presence of AlCl₃ as a catalyst. Generalexperimental procedure is described in J. Am. Chem. Soc., 60, 1938, p.1421, the disclosure of which is totally incoporated herein byreference. Purification is done by column chromatography. The actualpolymeric structure is obtained from this monomer, in situ, byillumination of the cell with visible light after the liquid crystalcomposition containing the monomer and initiator is prepared usingprocedures similar to that described in Example 9.

EXAMPLE 7 Preparation of a Device Containing Small Molecule LiquidCrystal Stabilizing Compound (1-I)

[0284] There was prepared a liquid crystal composition that included thefollowing:

[0285] 300 mg of BL118 (cholesteric liquid crystal reflecting at about580 nm);

[0286] 200 mg of BL087 (nematic liquid crystal, used to adjust thehelical pitch); and

[0287] 50 mg 4-NC—C₆H₄—N(n—C₁₀H₂₁)₂ (small molecule liquid crystalstabilizing compound).

[0288] The liquid crystal composition was homogenized by heating atabout 110° C. and by shaking, then allowed to cool down to roomtemperature. An empty 25 micrometer thick liquid crystal containmentstructure was fabricated by sealing two indium tin oxide (“ITO”)(transparent electrodes) glass coated slides. A small hole is kept inthe sealing to be used for filling the liquid crystal composition. Thecontainment structure was vacuum filled with the above liquid crystalcomposition, pressed and sealed. Immediately after preparation andbefore filling, the liquid crystal composition was in an essentiallyplanar state (quasi-planar), which was used to measure the reflectedwavelength of the prepared liquid crystal composition (which is anindirect measure of the helical pitch). The reflected wavelength was 960nm. After the first switching, the liquid crystal composition neverreached again the quasi-planar state, but was always in focal-conicstates. The liquid crystal composition changed to a homeotropic statewhen a voltage of about 80 Vrms was applied (sine wave, 60 Hz). When thevoltage was turned off, the liquid crystal composition went to the whitestate (focal-conic; small domains). When a voltage of 40-50 Vrms wasapplied, the liquid crystal composition switched to the transparentstate (focal-conic; large domains). When the voltage was turned off, theliquid crystal composition maintained the transparent state. Reflectancemeasurements were performed with the device having a black background.White reflectance was 11% and black reflectance was 1.6%. Contrast ratiowas 7/1. Both white and black states were stable for at least 4 days.

EXAMPLE 8

[0289] The procedures of Example 7 were followed except that thethickness for the space defined by the liquid crystal containmentstructures was varied to determine the switching voltage needed toachieve the white state (the higher voltage) for a particular spacethickness.

[0290] The results were as follows: Thickness (micrometers) SwitchingVoltage (Vrms) 25 82 V 20 67 V 15 54 V 10 38 V

EXAMPLE 9 Preparation of a Device Containing a Macromolecular LiquidCrystal Stabilizing Compound 2-II

[0291] There was prepared a liquid crystal composition that included thefollowing:

[0292] 96.5% liquid crystal mixture (BL118/BL087=65/35);

[0293] 3% CH₂═CH—COO—(CH₂)₆—O—C₆H₄—CN (polymerizable monomer); and

[0294] 0.5% camphoroquinone.

[0295] The liquid crystal composition was homogenized by light heating(to prevent polymerization initiation) and shaking. The composition wasprepared under yellow light, again in order to prevent polymerizationinitiation. A 25 micrometer liquid crystal containment structure wasprepared and filled with this composition using the procedures describedin other examples, pressed and fully sealed. Then it was exposed tovisible light (470 nm from a Xenon lamp, and by using appropriateoptical band-pass filter) for at least 30 min. The device was placedover a black background tested for switching. It switched white when 100V DC were applied then suddenly turned off the voltage. The whitereflectivity was 19%. It switched transparent (black because of theblack background) when 50-60 V DC was applied. It maintained the blackstate when the voltage was turned off. The contrast ratio was 7.5/1. Theblack state is stable (does not decay for at least 2 weeks). The whitestate maintained a good white reflectance for about 15 min. After thistime, the device required refreshing in order to maintain a good whitereflectance.

EXAMPLE 10 Preparation of a Device Containing a Dispersant

[0296] There was prepared a liquid crystal composition including thefollowing:

[0297] 95.5% liquid crystal mixture (BL118/BL087=60/40);

[0298] 3% CH₂═CH—COO—(CH₂)₆—O—C₆H₄—CN (polymerizable monomer);

[0299] 0.5% camphoroquinone; and

[0300] 1% sorbitan trioleate (SPAN 85;dispersant, commercially availableat Sigma-Aldrich).

[0301] A 25 micrometer liquid crystal containment structure containingthe liquid crystal composition was prepared by shaking the liquidcrystal composition and by slight heating (<60° C.) and filled with theliquid crystal composition using the procedures as described in otherexamples. The containment structure was exposed to 470 nm wavelengthlight for 1 hour. The device showed 17% white reflectivity, and acontrast ratio of 7/1. A high voltage of about 100 V DC was used. Afterturning off the high voltage, the liquid crystal composition was in thewhite state. A week after, the white reflectance was 14%. Forcomparison, a device made without dispersant as shown in EXAMPLE 9 hadonly 8% white reflectance a week after turning off the voltage.

EXAMPLE 11 Preparation of a Device Using a Non-Dipolar Co-Monomer

[0302] There was prepared a liquid crystal composition including thefollowing:

[0303] 96% liquid crystal mixture (BL118/BL087=60/40);

[0304] 3% CH₂═CH—COO—(CH₂)₆—O—C₆H₄—CN (polymerizable monomer);

[0305] 0.5% camphoroquinone; and

[0306] 0.5% SR9003 (propoxylated neopentyl glycol diacrylate;non-dipolar co-monomer, commercially available).

[0307] The liquid crystal composition was homogenized as described inExample 9. Then a 25 micrometer liquid crystal containment structure wasprepared and filled with the liquid crystal composition using theprocedures described in other examples and exposed to visible light (470nm) for 1 hour. The device switched homeotropic at 100 V DC, then whitewhen the voltage was turned off. It switched transparent (black on ablack background) when 50-60 V DC or AC was applied. Both white andstates were stable immediately after turning off the voltage, but thewhite started to decay as described in Example 9. The transparent statewas very uniform with no whitish spots. In contrast, some whitish spotswere visible in the transparent state when a comparison device wasprepared using the same procedures except that no co-monomer was used.

EXAMPLE 12

[0308] The same procedures of Example 11 were used except that theamount of the non-dipolar co-monomer was lower. A very uniform blackstate was obtained even when the amount of co-monomer was lower (forexample 0.2% of the overall liquid crystal composition) and no damagingeffect over the white state quality was observed.

EXAMPLE 13

[0309] Several devices containing the identical liquid crystalcomposition described below were prepared using the procedures ofExample 11, where such devices differed in the thickness of the spacedefined by the liquid crystal containment structure. The liquid crystalcomposition included the following:

[0310] 96% liquid crystal mixture (BL118/BL087=65/35);

[0311] 3% CH₂═CH—COO—(CH₂)₆—O—C₆H₄—CN (polymerizable monomer);

[0312] 0.5% camphoroquinone; and

[0313] 0.5% SR9003 (non-dipolar co-monomer, commercially available).

[0314] The results are shown below (switching was done with DC voltage;measurements of reflectance were done with a black background):Thickness (micrometers) Vwhite Vblack White reflectance 25 102 V  65 V19% 20 82 V 45 V 17% 15 63 V 30 V 13% 10 42 V 25 V 10%

EXAMPLE 14 Preparation of a Device Containing Both Dispersant andNon-Dipolar Co-Monomer

[0315] There was prepared a liquid crystal composition which includedthe following:

[0316] 96% liquid crystal mixture (BL118/BL087=65/35);

[0317] 3% CH₂═CH—COO—(CH₂)₆—O—C₆H₄—CN (polymerizable monomer);

[0318] 0.5% camphoroquinone; 0.5% SR9003 (non-dipolar co-monomer,commercially available); and 1% SPAN 85 (dispersant).

[0319] The liquid crystal composition was homogenized as described inExample 9. A liquid crystal containment structure was prepared andfilled with the liquid crystal composition using the proceduresdescribed in other examples. After sealing, the liquid crystalcomposition is exposed for 1 hour to 470 nm wavelength light. The deviceswitches at about 100 V to achieve stable white state when the voltageis turned off. The device switches to a transparent state when a voltageof 50-70 V is applied. This state is uniformly transparent and stableafter the voltage is turned off.

We claim:
 1. A compound having formula (2)

wherein A2 is an electron acceptor moiety; C2 is a conjugated bridgingmoiety; D2 is an electron donor moiety; S2 is a hydrocarbon, aheterocyclic moiety, or a hetero-acyclic moiety; a′ is an integer; Z2 isa polymerizable moiety; and e′ is the degree of polymerization.
 2. Thecompound of claim 1, wherein A2 is selected from the group consistingof: (a) an aldehyde; (b) a ketone; (c) an ester; (d) a carboxylic acid;(e) cyano; (f) nitro; (g) nitroso; (h) a sulfur-based group; (i) afluorine atom; (j) an alkene; and (k) a boron atom.
 3. The compound ofclaim 1, wherein C2 is selected from the group consisting of: (a) atleast one aromatic ring; (b) at least one aromatic ring conjugatedthrough one or more ethenyl or ethynyl bonds; and (c) fused aromaticrings.
 4. The compound of claim 1, wherein D2 is selected from the groupconsisting of: (a) an atom selected from the group consisting of N, O,S, and P, where the valence of the atom is satisfied by bonding with S2and C2 and optionally with Z2; (b) an atom selected from the groupconsisting of N, O, S, and P bonded to S2 and C2, and optionally withZ2, where the atom also is bonded to at least one other moiety tosatisfy the valence of the atom; (c) ferrocenyl; (d) azulenyl; and (e)at least one aromatic heterocyclic ring.
 5. The compound of claim 1,wherein the hydrocarbon of S2 is selected from the group consisting of:(a) a straight chain alkyl group; (b) a branched alkyl group; (c) atleast one cycloalkyl group, optionally substituted with an alkyl group,an arylalkyl group, an alkylaryl group, a cycloalkyl group, or analkylcycloalkyl group; and (d) an arylalkyl group or an alkylaryl group.6. The compound of claim 1, wherein S2 includes a liquid crystal moiety.7. The compound of claim 1, wherein Z2 is selected from the groupconsisting of: H₂C═CH—C(O)—O— (acryl), H₂C═C(CH₃)—C(O)—O— (methacryl),H₂C═C(C₂H₅)C(O)O— (ethacryl), —CH═CH₂ (vinyl), and —C(CH₃)═CH₂.
 8. Thecompound of claim 1, wherein Z2 includes a substitution with a moietyselected from the group consisting of: (a) an alkyl chain; and (b) asubstituted alkyl chain selected from the group consisting of: analkoxy, a halide substituted alkyl group, and an amino-alkyl group. 9.The compound of claim 1, wherein the compound of formula (2) is selectedfrom the group consisting of:

wherein A2, C2, D2, S2, and Z2 are indicated.
 10. A compositioncomprising a liquid crystal and a compound having formula (2)

wherein A2 is an electron acceptor moiety; C2 is a conjugated bridgingmoiety; D2 is an electron donor moiety; S2 is a liquid crystalcompatibilizing moiety; a′ is an integer; Z2 is a polymerizable moiety;and e′ is the degree of polymerization.
 11. The composition of claim 10,wherein A2 is selected from the group consisting of: (a) an aldehyde;(b) a ketone; (c) an ester; (d) a carboxylic acid; (e) cyano; (f) nitro;(g) nitroso; (h) a sulfur-based group; (i) a fluorine atom; (j) analkene; and (k) a boron atom.
 12. The composition of claim 10, whereinC2 is selected from the group consisting of: (a) at least one aromaticring; (b) at least one aromatic ring conjugated through one or moreethenyl or ethynyl bonds; and (c) fused aromatic rings.
 13. Thecomposition of claim 10, wherein D2 is selected from the groupconsisting of: (a) an atom selected from the group consisting of N, O,S, and P, where the valence of the atom is satisfied by bonding with S2and C2 and optionally with Z2; (b) an atom selected from the groupconsisting of N, O, S, and P bonded to S2 and C2, and optionally withZ2, where the atom also is bonded to at least one other moiety tosatisfy the valence of the atom; (c) ferrocenyl; (d) azulenyl; and (e)at least one aromatic heterocyclic ring.
 14. The composition of claim10, wherein S2 is a hydrocarbon selected from the group consisting of:(a) a straight chain alkyl group; (b) a branched alkyl group; (c) atleast one cycloalkyl group, optionally substituted with an alkyl group,an arylalkyl group, an alkylaryl group, a cycloalkyl group, or analkylcycloalkyl group; and (d) an arylalkyl group or an alkylaryl group.15. The composition of claim 10, wherein S2 includes a liquid crystalmoiety.
 16. The composition of claim 10, wherein Z2 is selected from thegroup consisting of: H₂C═CH—C(O)—O— (acryl), H₂C═C(CH₃)—C(O)—O—(methacryl), H₂C═C(C₂H₅)—C(O)O— (ethacryl), CH═CH₂ (vinyl), and—C(CH₃)═CH₂.
 17. The composition of claim 10, wherein Z2 includes asubstitution with a moiety selected from the group consisting of: (a) analkyl chain; and (b) a substituted alkyl chain selected from the groupconsisting of: an alkoxy, a halide substituted alkyl group, and anamino-alkyl group.
 18. The composition of claim 10, wherein the compoundof formula (2) is selected from the group consisting of:

wherein A2, C2, D2, S2, and Z2 are indicated.
 19. A device comprising: aliquid crystal composition including a liquid crystal and a liquidcrystal domain stabilizing compound, wherein the liquid crystalcomposition is switchable between a strongly scattering state of a firstplurality of smaller liquid crystal domains that strongly scatters apredetermined light and a weakly scattering state of a second pluralityof larger liquid crystal domains that weakly scatters the predeterminedlight; and a liquid crystal containment structure defining a space forthe liquid crystal composition, wherein the liquid crystal domainstabilizing compound is a compound having formula (2)

wherein A2 is an electron acceptor moiety; C2 is a conjugated bridgingmoiety; D2 is an electron donor moiety; S2 is a liquid crystalcompatibilizing moiety; a′ is an integer; Z2 is a polymerizable moiety;and e′ is the degree of polymerization.
 20. The device of claim 19,wherein the weakly scattering state is stable and the stronglyscattering state is stable.
 21. The device of claim 19, furthercomprising: an electric field generating apparatus that electricallyinduces the change of the strongly scattering state to the weaklyscattering state, and the change of the weakly scattering state to thestrongly scattering state.
 22. The device of claim 19, further includinga colored surface positioned to absorb a portion of the predeterminedlight that passes through the liquid crystal composition in the weaklyscattering state such that an observer sees a predetermined color. 23.The device of claim 19, further including a receiver.
 24. The device ofclaim 19, wherein the structure is substantially transparent to thepredetermined light to allow entry of the predetermined light into thestructure, through the liquid crystal composition, and exit of thepredetermined light from the structure in the weakly scattering state.25. The device of claim 19, wherein the liquid crystal in both thesmaller liquid crystal domains and the larger liquid crystal domainspossesses helical axes that are randomly oriented.